diff --git a/common.json b/common.json
index 500a16f186d7..2ad62cc0e20d 100644
--- a/common.json
+++ b/common.json
@@ -4,7 +4,7 @@
     "Jsonnet files should not include this file directly but use ci/common.jsonnet instead."
   ],
 
-  "mx_version": "7.36.1",
+  "mx_version": "7.36.5",
 
   "COMMENT.jdks": "When adding or removing JDKs keep in sync with JDKs in ci/common.jsonnet",
   "jdks": {
diff --git a/compiler/mx.compiler/suite.py b/compiler/mx.compiler/suite.py
index a85fe56f4aed..44e3d98e945d 100644
--- a/compiler/mx.compiler/suite.py
+++ b/compiler/mx.compiler/suite.py
@@ -212,7 +212,7 @@
         "GRAAL_PROCESSOR"
       ],
       "checkPackagePrefix": "false",
-      "checkstyleVersion" : "10.7.0",
+      "checkstyleVersion" : "10.21.0",
       "javaCompliance" : "21+",
       "workingSets" : "API,Graal",
       "jacoco" : "include",
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/api/directives/test/BlackholeDirectiveTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/api/directives/test/BlackholeDirectiveTest.java
index 470411b99ec6..f1b4efbf59f5 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/api/directives/test/BlackholeDirectiveTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/api/directives/test/BlackholeDirectiveTest.java
@@ -103,7 +103,7 @@ public void testInt() {
         test("blackholeIntSnippet", 17);
     }
 
-    private static class Dummy {
+    private static final class Dummy {
         private int x = 42;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/api/directives/test/OpaqueDirectiveTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/api/directives/test/OpaqueDirectiveTest.java
index 18c06d2f9a18..be08f1d885f5 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/api/directives/test/OpaqueDirectiveTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/api/directives/test/OpaqueDirectiveTest.java
@@ -108,7 +108,7 @@ public void testDouble() {
         test("opaqueDoubleSnippet");
     }
 
-    private static class Dummy {
+    private static final class Dummy {
     }
 
     @OpaqueSnippet(expectedReturnNode = ConstantNode.class)
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/CompilationResultTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/CompilationResultTest.java
index 85f6fe07db0d..5b29279d32b7 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/CompilationResultTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/CompilationResultTest.java
@@ -77,7 +77,7 @@ public void testCompilationResult() {
         assertTrue(result.toString().length() > 0); // test for NPE
     }
 
-    private static class TestMarkId implements CompilationResult.MarkId {
+    private static final class TestMarkId implements CompilationResult.MarkId {
         @Override
         public String getName() {
             return "test";
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/ConditionalEliminationTest10.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/ConditionalEliminationTest10.java
index 26503412dc8d..09cbb937c293 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/ConditionalEliminationTest10.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/ConditionalEliminationTest10.java
@@ -47,7 +47,7 @@ public class ConditionalEliminationTest10 extends ConditionalEliminationTestBase
     private static boolean condition1;
     private static boolean condition2;
 
-    private static class TestClass {
+    private static final class TestClass {
         int x;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/DegeneratedLoopsTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/DegeneratedLoopsTest.java
index b0510d27c01e..85dac4c9af79 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/DegeneratedLoopsTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/DegeneratedLoopsTest.java
@@ -50,7 +50,7 @@ public void test1() {
         test("test1Snippet");
     }
 
-    private static class UnresolvedException extends RuntimeException {
+    private static final class UnresolvedException extends RuntimeException {
 
         private static final long serialVersionUID = 5215434338750728440L;
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/NodePropertiesTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/NodePropertiesTest.java
index 572ff76d3881..bafad149d11f 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/NodePropertiesTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/NodePropertiesTest.java
@@ -318,7 +318,7 @@ public void simplify(Node node, SimplifierTool tool) {
         }
     }
 
-    private static class GraphCostPhase extends TestBasePhase<CoreProviders> {
+    private static final class GraphCostPhase extends TestBasePhase<CoreProviders> {
         private double finalCycles;
         private double finalSize;
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/VerifyAssertionUsageTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/VerifyAssertionUsageTest.java
index 3cadb2349bf9..e1bd5c39d6ab 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/VerifyAssertionUsageTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/VerifyAssertionUsageTest.java
@@ -87,7 +87,7 @@ public static void afterClass() {
     /**
      * Valid call with an assertion message.
      */
-    private static class ValidAssertUsage1 extends TestPhase {
+    private static final class ValidAssertUsage1 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             assert graph.hasLoops() : "Must have loops";
@@ -98,7 +98,7 @@ protected void run(StructuredGraph graph) {
      * Valid call with a trivial condition. Null check is trivial in that if it fails the error is
      * "clear" to spot by inspecting the code.
      */
-    private static class ValidAssertUsage2 extends TestPhase {
+    private static final class ValidAssertUsage2 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             assert graph != null;
@@ -108,7 +108,7 @@ protected void run(StructuredGraph graph) {
     /**
      * Valid usage of known assertion methods that are always safe to call.
      */
-    private static class ValidAssertUsage3 extends TestPhase {
+    private static final class ValidAssertUsage3 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             assert GraphOrder.assertSchedulableGraph(graph);
@@ -119,7 +119,7 @@ protected void run(StructuredGraph graph) {
     /**
      * Invalid assertion call: missing assertion message.
      */
-    private static class InvalidAssertUsage extends TestPhase {
+    private static final class InvalidAssertUsage extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             assert graph.hasLoops();
@@ -131,7 +131,7 @@ protected void run(StructuredGraph graph) {
      * further but call further eventually calls a method with an assertion error message so the
      * assertion usage is correct several levels down the call graph.
      */
-    private static class ValidCallGraphUsage1 extends TestPhase {
+    private static final class ValidCallGraphUsage1 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             assert verifyGraph(graph);
@@ -160,7 +160,7 @@ private static boolean callFurther1(StructuredGraph g) {
      * Invalid call: call further is missing the assertion message and run calls callFurther so this
      * is a missing assertion message 1 level down the call graph.
      */
-    private static class InvalidCallGraphUsage1 extends TestPhase {
+    private static final class InvalidCallGraphUsage1 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             assert callFurther(graph);
@@ -182,7 +182,7 @@ private static boolean callFurther(StructuredGraph g) {
      * Invalid call graph usage: multiple calls to methods without an error message a second level
      * down the call graph.
      */
-    private static class InvalidCallGraphUsage2 extends TestPhase {
+    private static final class InvalidCallGraphUsage2 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             assert callFurther(graph);
@@ -207,7 +207,7 @@ private static boolean callFurther(StructuredGraph g) {
      * superfluous: callFurther does assertion checking and will always return true - thus the error
      * message in run is never used.
      */
-    private static class InvalidCallGraphUsage3 extends TestPhase {
+    private static final class InvalidCallGraphUsage3 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             assert callFurther(graph) : "Invalid superfluous message";
@@ -235,7 +235,7 @@ private static boolean callFurther1(StructuredGraph g) {
     /**
      * Same as {@link InvalidCallGraphUsage3} but without multiple levels.
      */
-    private static class InvalidCallGraphUsage31 extends TestPhase {
+    private static final class InvalidCallGraphUsage31 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             assert verifyGraph(graph) : "Invalid superfluous message";
@@ -254,7 +254,7 @@ private static boolean verifyGraph(StructuredGraph graph) {
      * the caller. Specifically assertSth has a return false path that would fire the error in the
      * caller run without a message.
      */
-    private static class InvalidCallGraphUsage4 extends TestPhase {
+    private static final class InvalidCallGraphUsage4 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             assert assertSth(graph);
@@ -282,7 +282,7 @@ private static boolean assertSth1(StructuredGraph g) {
     /**
      * Invalid assertion usage: the path doSth() does not assert anything.
      */
-    private static class InvalidCallGraphUsage5 extends TestPhase {
+    private static final class InvalidCallGraphUsage5 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             assert assertSth(graph);
@@ -304,7 +304,7 @@ static void doSth() {
      * - the paths where they are missing them is loop iterations so those are fine. They still
      * return {@code true} on all paths.
      */
-    private static class ValidCallGraphUsage5 extends TestPhase {
+    private static final class ValidCallGraphUsage5 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             assert assertSth(graph);
@@ -339,7 +339,7 @@ private static boolean assertSth2(StructuredGraph g) {
      * Correct assertion usage: calling another method not via an assert but regularly where that
      * method itself calls an assertion.
      */
-    private static class ValidCallGraphUsage6 extends TestPhase {
+    private static final class ValidCallGraphUsage6 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             assert assertSth(graph);
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/VerifyBailoutUsageTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/VerifyBailoutUsageTest.java
index a6dcc7c721e6..fe4a62b987de 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/VerifyBailoutUsageTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/VerifyBailoutUsageTest.java
@@ -53,35 +53,35 @@
 
 public class VerifyBailoutUsageTest {
 
-    private static class InvalidBailoutUsagePhase1 extends TestPhase {
+    private static final class InvalidBailoutUsagePhase1 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             throw new BailoutException("Bailout in graph %s", graph);
         }
     }
 
-    private static class InvalidBailoutUsagePhase2 extends TestPhase {
+    private static final class InvalidBailoutUsagePhase2 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             throw new BailoutException(new GraalError("other cause"), "Bailout in graph %s", graph);
         }
     }
 
-    private static class InvalidBailoutUsagePhase3 extends TestPhase {
+    private static final class InvalidBailoutUsagePhase3 extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             throw new BailoutException(true/* permanent */, "Bailout in graph %s", graph);
         }
     }
 
-    private static class ValidPermanentBailoutUsage extends TestPhase {
+    private static final class ValidPermanentBailoutUsage extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             throw new PermanentBailoutException("Valid permanent bailout %s", graph);
         }
     }
 
-    private static class ValidRetryableBailoutUsage extends TestPhase {
+    private static final class ValidRetryableBailoutUsage extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             throw new RetryableBailoutException("Valid retryable bailout %s", graph);
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/VerifyDebugUsageTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/VerifyDebugUsageTest.java
index d7500c7263f3..e3982f327814 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/VerifyDebugUsageTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/VerifyDebugUsageTest.java
@@ -54,7 +54,7 @@
 
 public class VerifyDebugUsageTest {
 
-    private static class InvalidLogUsagePhase extends TestPhase {
+    private static final class InvalidLogUsagePhase extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             DebugContext debug = graph.getDebug();
@@ -65,7 +65,7 @@ protected void run(StructuredGraph graph) {
 
     }
 
-    private static class InvalidLogAndIndentUsagePhase extends TestPhase {
+    private static final class InvalidLogAndIndentUsagePhase extends TestPhase {
         @Override
         @SuppressWarnings("try")
         protected void run(StructuredGraph graph) {
@@ -107,7 +107,7 @@ int getLevel() {
         }
     }
 
-    private static class InvalidVerifyUsagePhase extends TestPhase {
+    private static final class InvalidVerifyUsagePhase extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             DebugContext debug = graph.getDebug();
@@ -116,7 +116,7 @@ protected void run(StructuredGraph graph) {
 
     }
 
-    private static class InvalidConcatLogUsagePhase extends TestPhase {
+    private static final class InvalidConcatLogUsagePhase extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             DebugContext debug = graph.getDebug();
@@ -127,7 +127,7 @@ protected void run(StructuredGraph graph) {
 
     }
 
-    private static class InvalidConcatLogAndIndentUsagePhase extends TestPhase {
+    private static final class InvalidConcatLogAndIndentUsagePhase extends TestPhase {
         @Override
         @SuppressWarnings("try")
         protected void run(StructuredGraph graph) {
@@ -218,14 +218,14 @@ protected void run(StructuredGraph graph) {
 
     public static Object sideEffect;
 
-    private static class InvalidGraalErrorCtorPhase extends TestPhase {
+    private static final class InvalidGraalErrorCtorPhase extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             sideEffect = new GraalError("No Error %s", graph.toString());
         }
     }
 
-    private static class ValidGraalErrorCtorPhase extends TestPhase {
+    private static final class ValidGraalErrorCtorPhase extends TestPhase {
         @Override
         protected void run(StructuredGraph graph) {
             sideEffect = new GraalError("Error %s", graph);
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/deopt/MonitorDeoptTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/deopt/MonitorDeoptTest.java
index cf7683a30e75..6da74c71b219 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/deopt/MonitorDeoptTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/deopt/MonitorDeoptTest.java
@@ -55,7 +55,7 @@ private enum State {
 
     static final long TIMEOUT = 5000;
 
-    private static class Monitor {
+    private static final class Monitor {
         private volatile State state = State.INITIAL;
 
         public synchronized void setState(State newState) {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/inlining/ImpreciseArgumentStampInliningTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/inlining/ImpreciseArgumentStampInliningTest.java
index 798c6cf70f8f..fa30902e6923 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/inlining/ImpreciseArgumentStampInliningTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/core/test/inlining/ImpreciseArgumentStampInliningTest.java
@@ -60,7 +60,7 @@
  */
 public class ImpreciseArgumentStampInliningTest extends GraalCompilerTest {
 
-    private static class InlineMethodHolder {
+    private static final class InlineMethodHolder {
         static void inlineMe(UnresolveableClass argument) {
             GraalDirectives.blackhole(argument);
         }
@@ -76,7 +76,7 @@ public static void snippet() {
     }
 
     // Will be unresolved during bytecode parsing, and resolved during inlining.
-    private static class UnresolveableClass {
+    private static final class UnresolveableClass {
     }
 
     @Test
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/ArrayNewInstanceTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/ArrayNewInstanceTest.java
index 37f056cd11e1..5eb83da96799 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/ArrayNewInstanceTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/ArrayNewInstanceTest.java
@@ -102,7 +102,7 @@ public void testNewArrayInLoop() {
         assertTrue(box.inCompiledCode != shouldDeopt);
     }
 
-    private static class DeoptimizationBox {
+    private static final class DeoptimizationBox {
         volatile boolean inCompiledCode = false;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/ClassSubstitutionsTests.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/ClassSubstitutionsTests.java
index d95354cae749..779bcad01c0c 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/ClassSubstitutionsTests.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/ClassSubstitutionsTests.java
@@ -208,10 +208,10 @@ public boolean fieldIsArray() {
     private static class A {
     }
 
-    private static class B extends A {
+    private static final class B extends A {
     }
 
-    private static class C {
+    private static final class C {
     }
 
     private static final A aInstance = new A();
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/ExplicitExceptionTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/ExplicitExceptionTest.java
index 74216599fea2..0980a6447ede 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/ExplicitExceptionTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/ExplicitExceptionTest.java
@@ -102,7 +102,7 @@ public void testNPEArray() {
         test("testNPEArraySnippet", array);
     }
 
-    private static class TestClass {
+    private static final class TestClass {
         int field;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/HotSpotMethodSubstitutionTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/HotSpotMethodSubstitutionTest.java
index 71c8819bd98f..2a4cceec053d 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/HotSpotMethodSubstitutionTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/HotSpotMethodSubstitutionTest.java
@@ -170,7 +170,7 @@ public static int systemIdentityHashCode(Object obj) {
         return System.identityHashCode(obj);
     }
 
-    private static class TestClassA {
+    private static final class TestClassA {
     }
 
     public static String testCallSiteGetTargetSnippet(int i) throws Exception {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/JVMCIInfopointErrorTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/JVMCIInfopointErrorTest.java
index 7e2c4178b0d7..4f5d3d63909f 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/JVMCIInfopointErrorTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/JVMCIInfopointErrorTest.java
@@ -276,7 +276,7 @@ public void testUnexpectedObject() {
         });
     }
 
-    private static class UnknownJavaValue implements JavaValue {
+    private static final class UnknownJavaValue implements JavaValue {
     }
 
     @SuppressWarnings("try")
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/PolymorphicInliningTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/PolymorphicInliningTest.java
index 64bee38dd1f5..6652366c6c96 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/PolymorphicInliningTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/PolymorphicInliningTest.java
@@ -156,21 +156,21 @@ private abstract static class SuperClass {
         abstract int foo();
     }
 
-    private static class A extends SuperClass {
+    private static final class A extends SuperClass {
         @Override
         public int foo() {
             return 'A';
         }
     }
 
-    private static class B extends SuperClass {
+    private static final class B extends SuperClass {
         @Override
         public int foo() {
             return 'B';
         }
     }
 
-    private static class NotInlinableSubClass extends SuperClass {
+    private static final class NotInlinableSubClass extends SuperClass {
         @Override
         public int foo() {
             return 'X';
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/VirtualThreadJFRTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/VirtualThreadJFRTest.java
index 75d3ca62381e..9cb322612ce4 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/VirtualThreadJFRTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/hotspot/test/VirtualThreadJFRTest.java
@@ -50,7 +50,7 @@ public class VirtualThreadJFRTest extends SubprocessTest {
     private static final int STARTER_THREADS = 10;
 
     @Name("test.Tester")
-    private static class TestEvent extends Event {
+    private static final class TestEvent extends Event {
     }
 
     private static boolean isJFRAvailable() {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_checkcast01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_checkcast01.java
index 7d6355099e2f..1593f4338f1b 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_checkcast01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_checkcast01.java
@@ -31,7 +31,7 @@
  */
 public class BC_checkcast01 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
     }
 
     static Object object2 = new Object();
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_checkcast02.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_checkcast02.java
index 668b022c1e72..4ddb5e1eda65 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_checkcast02.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_checkcast02.java
@@ -31,7 +31,7 @@
  */
 public class BC_checkcast02 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
     }
 
     static Object[] o1 = {new Object()};
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_checkcast03.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_checkcast03.java
index 61c379ad3089..d495c951e4db 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_checkcast03.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_checkcast03.java
@@ -40,7 +40,7 @@ private static class BaseClass {
 
     }
 
-    private static class TestClass extends BaseClass implements IObject {
+    private static final class TestClass extends BaseClass implements IObject {
     }
 
     static TestClass[] a1 = {new TestClass()};
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_instanceof.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_instanceof.java
index e35a02f54f95..5e40e6e75000 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_instanceof.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_instanceof.java
@@ -31,7 +31,7 @@
  */
 public class BC_instanceof extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
     }
 
     static Object object2 = new Object();
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_instanceof01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_instanceof01.java
index 2f418d0860ed..70d63f496866 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_instanceof01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_instanceof01.java
@@ -48,10 +48,10 @@ private static class BaseClass {
 
     }
 
-    private static class TestClass extends BaseClass implements IObject {
+    private static final class TestClass extends BaseClass implements IObject {
     }
 
-    private static class DerivedTestClass extends BaseClass implements IDerivedObject {
+    private static final class DerivedTestClass extends BaseClass implements IDerivedObject {
 
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_invokespecial.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_invokespecial.java
index 810d9b734033..3c3e27141d7e 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_invokespecial.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_invokespecial.java
@@ -31,7 +31,7 @@
  */
 public class BC_invokespecial extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         @SuppressWarnings("static-method")
         private int id(int i) {
             return i;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_invokespecial2.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_invokespecial2.java
index d375164a9160..b4f9fe130053 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_invokespecial2.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_invokespecial2.java
@@ -34,7 +34,7 @@
  */
 public class BC_invokespecial2 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         @SuppressWarnings("static-method")
         private int id(int i) {
             return 4 + i;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_invokevirtual.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_invokevirtual.java
index 1a1e34faeb39..68b10471c628 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_invokevirtual.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_invokevirtual.java
@@ -31,7 +31,9 @@
  */
 public class BC_invokevirtual extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
+
+        @SuppressWarnings("static-method")
         public int id(int i) {
             return i;
         }
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_01.java
index f49c0d033d90..26264f4393aa 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_01.java
@@ -31,7 +31,7 @@
  */
 public class BC_putfield_01 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         private int field;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_02.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_02.java
index 32e1b6dcf1f8..cdc42361e135 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_02.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_02.java
@@ -31,7 +31,7 @@
  */
 public class BC_putfield_02 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         private Object field;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_03.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_03.java
index 510831a87f83..63094a410e10 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_03.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_03.java
@@ -31,7 +31,7 @@
  */
 public class BC_putfield_03 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         private volatile int field;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_04.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_04.java
index 32e67048dd1a..d9758a01822c 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_04.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/bytecode/BC_putfield_04.java
@@ -31,7 +31,7 @@
  */
 public class BC_putfield_04 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         private volatile Object field;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_getfield.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_getfield.java
index 6ae781e17926..efce8203892b 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_getfield.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_getfield.java
@@ -32,7 +32,7 @@
 
 public class BC_getfield extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         private int field = 13;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_getfield1.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_getfield1.java
index b23857ba69e8..148c772bf71d 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_getfield1.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_getfield1.java
@@ -38,7 +38,7 @@ protected OptimisticOptimizations getOptimisticOptimizations() {
         return OptimisticOptimizations.NONE;
     }
 
-    private static class TestClass {
+    private static final class TestClass {
         private int field = 13;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_invokespecial01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_invokespecial01.java
index a04ea9895b69..aeb54b571ed9 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_invokespecial01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_invokespecial01.java
@@ -32,7 +32,7 @@
  */
 public class BC_invokespecial01 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         @SuppressWarnings("static-method")
         private boolean method() {
             return true;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_invokevirtual01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_invokevirtual01.java
index 57aeb0e6dd1b..896229d0a4ce 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_invokevirtual01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_invokevirtual01.java
@@ -32,7 +32,8 @@
  */
 public class BC_invokevirtual01 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
+        @SuppressWarnings("static-method")
         public boolean method() {
             return true;
         }
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_invokevirtual02.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_invokevirtual02.java
index 5f1ee8c31d79..690246a53696 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_invokevirtual02.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_invokevirtual02.java
@@ -32,9 +32,9 @@
  */
 public class BC_invokevirtual02 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         @SuppressWarnings("static-method")
-        public final boolean method() {
+        public boolean method() {
             return true;
         }
     }
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_putfield.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_putfield.java
index 4c884108b96d..4293096e4916 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_putfield.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/BC_putfield.java
@@ -32,7 +32,7 @@
 
 public class BC_putfield extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         private int field;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized01.java
index ece7667ca745..f1fd4ea3f9d8 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized01.java
@@ -32,7 +32,7 @@
  */
 public class Except_Synchronized01 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         final int x = 1;
 
         @SuppressWarnings("all")
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized02.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized02.java
index b169c5f9daad..b024038c900d 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized02.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized02.java
@@ -32,7 +32,7 @@
 
 public class Except_Synchronized02 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
 
         final int x = 1;
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized03.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized03.java
index 65351b0fff76..9b74ca6278fb 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized03.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized03.java
@@ -32,7 +32,7 @@
  */
 public class Except_Synchronized03 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         int x = 1;
 
         @SuppressWarnings("all")
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized04.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized04.java
index fa4668ef840d..fb22dbd46bf0 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized04.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Except_Synchronized04.java
@@ -32,7 +32,7 @@
 
 public class Except_Synchronized04 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
 
         final int x = 1;
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Throw_Synchronized04.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Throw_Synchronized04.java
index 81e8ba182945..629966b2228b 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Throw_Synchronized04.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Throw_Synchronized04.java
@@ -32,8 +32,8 @@
 
 public class Throw_Synchronized04 extends JTTTest {
 
-    private static class TestClass {
-        @SuppressWarnings("unused")
+    private static final class TestClass {
+        @SuppressWarnings({"unused", "static-method"})
         public synchronized boolean test2(int i) throws Exception {
             throw new Exception();
         }
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Throw_Synchronized05.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Throw_Synchronized05.java
index cea2926691f2..c43c3d7935b8 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Throw_Synchronized05.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/Throw_Synchronized05.java
@@ -32,8 +32,8 @@
 
 public class Throw_Synchronized05 extends JTTTest {
 
-    private static class TestClass {
-        @SuppressWarnings("unused")
+    private static final class TestClass {
+        @SuppressWarnings({"unused", "static-method"})
         public synchronized boolean test2(int i) throws Exception {
             try {
                 throw new Exception();
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/UntrustedInterfaces.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/UntrustedInterfaces.java
index 78559e9d837a..fe388c7809f0 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/UntrustedInterfaces.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/except/UntrustedInterfaces.java
@@ -217,7 +217,7 @@ public void testReturn2() {
         runTest("returnCheckcast", poisonPill);
     }
 
-    private static class PoisonLoader extends ExportingClassLoader {
+    private static final class PoisonLoader extends ExportingClassLoader {
         public static final String POISON_IMPL_NAME = "jdk.graal.compiler.jtt.except.PoisonPill";
 
         @Override
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/jdk/UnsafeAccess01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/jdk/UnsafeAccess01.java
index 6664e80bc418..523cef07aa6d 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/jdk/UnsafeAccess01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/jdk/UnsafeAccess01.java
@@ -47,7 +47,7 @@ public class UnsafeAccess01 extends JTTTest {
         offset = UNSAFE.objectFieldOffset(field);
     }
 
-    private static class TestClass {
+    private static final class TestClass {
         private int field = 42;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Bridge_method01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Bridge_method01.java
index 26e0833eb6d2..42f2723ba6f5 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Bridge_method01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Bridge_method01.java
@@ -37,7 +37,7 @@ private abstract static class Wrap<T> {
         abstract T get();
     }
 
-    private static class IWrap extends Wrap<Integer> {
+    private static final class IWrap extends Wrap<Integer> {
 
         @Override
         Integer get() {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Class_getModifiers01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Class_getModifiers01.java
index eddade33835e..e625a59b2e8d 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Class_getModifiers01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Class_getModifiers01.java
@@ -32,13 +32,13 @@
 
 public final class Class_getModifiers01 extends JTTTest {
 
-    private static class PrivateStatic {
+    private static final class PrivateStatic {
     }
 
     private static final class PrivateStaticFinal {
     }
 
-    private static class Private {
+    private static final class Private {
     }
 
     public static int test(Class<?> c) {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Class_isInstance06.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Class_isInstance06.java
index 6001341b1aeb..3ae86c5dba33 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Class_isInstance06.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Class_isInstance06.java
@@ -32,7 +32,7 @@
 
 public final class Class_isInstance06 extends JTTTest {
 
-    private static class TestClass implements Cloneable {
+    private static final class TestClass implements Cloneable {
     }
 
     static final String string = "";
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_clone01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_clone01.java
index 97831723e1e4..3f41dcccf880 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_clone01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_clone01.java
@@ -32,7 +32,7 @@
 
 public class Object_clone01 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         @SuppressWarnings("unused")
         private boolean tryClone(int i) throws CloneNotSupportedException {
             return this == this.clone();
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_clone02.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_clone02.java
index b344fd7dfbda..4a511fcd057b 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_clone02.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_clone02.java
@@ -32,7 +32,7 @@
 
 public class Object_clone02 extends JTTTest {
 
-    private static class TestClass implements Cloneable {
+    private static final class TestClass implements Cloneable {
         @SuppressWarnings("unused")
         private boolean tryClone(int i) throws CloneNotSupportedException {
             return this == this.clone();
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_toString01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_toString01.java
index 2d55f2b363d4..0ff0d23ccb5a 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_toString01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_toString01.java
@@ -32,7 +32,7 @@
 
 public class Object_toString01 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         @Override
         public String toString() {
             return string;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_toString02.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_toString02.java
index 8a1c9e64c3a8..f8d4fde77b29 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_toString02.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/lang/Object_toString02.java
@@ -35,7 +35,7 @@
 
 public class Object_toString02 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         @Override
         public String toString() {
             return "XYZ";
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/Conditional01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/Conditional01.java
index e7ab30926f22..e6f2ed528cfa 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/Conditional01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/Conditional01.java
@@ -35,7 +35,7 @@
 @SuppressWarnings("unused")
 public class Conditional01 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         private int nextPC;
         private int pc;
         private boolean aC;
@@ -75,11 +75,11 @@ public int getRegisterByte(Register r1) {
             return r1.val;
         }
 
-        public int low(int tmp3) {
+        public static int low(int tmp3) {
             return tmp3 & 0x01;
         }
 
-        public int bit(boolean c2) {
+        public static int bit(boolean c2) {
             return c2 ? 1 : 0;
         }
     }
@@ -109,13 +109,13 @@ public static int test(int arg) {
         return c.cyclesConsumed;
     }
 
-    private static class Register {
+    private static final class Register {
 
         int val;
         int num;
     }
 
-    private static class CPC {
+    private static final class CPC {
 
         public Register r1;
         public Register r2;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/Fold_Cast01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/Fold_Cast01.java
index b157bf811c19..552e392a4630 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/Fold_Cast01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/Fold_Cast01.java
@@ -32,7 +32,7 @@
  */
 public class Fold_Cast01 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         int field = 9;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/GuardMovement.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/GuardMovement.java
index ac840da9f702..efc781213561 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/GuardMovement.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/GuardMovement.java
@@ -36,7 +36,7 @@ public class GuardMovement extends JTTTest {
 
     private static int staticValue;
 
-    private static class A {
+    private static final class A {
         int x;
         int y;
     }
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/LLE_01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/LLE_01.java
index 4d897c294c2c..9a3ca274fc3b 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/LLE_01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/LLE_01.java
@@ -34,7 +34,7 @@
  */
 public class LLE_01 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         int field1;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/List_reorder_bug.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/List_reorder_bug.java
index 0696b8ab72cd..e06d2c339ff4 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/List_reorder_bug.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/List_reorder_bug.java
@@ -32,7 +32,7 @@
 @SuppressWarnings("unused")
 public class List_reorder_bug extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         String s;
 
         private void print(String s2) {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/NCE_01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/NCE_01.java
index 925cf87fecdd..33b796b73873 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/NCE_01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/NCE_01.java
@@ -32,7 +32,7 @@
  */
 public class NCE_01 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         int field1 = 22;
         int field2 = 23;
     }
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/SchedulingBug_01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/SchedulingBug_01.java
index 756a711f199a..13750d99311d 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/SchedulingBug_01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/SchedulingBug_01.java
@@ -31,7 +31,7 @@
  */
 public class SchedulingBug_01 extends JTTTest {
 
-    private static class VolatileBoxHolder {
+    private static final class VolatileBoxHolder {
         volatile Integer box;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Cast01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Cast01.java
index 60665131e01d..5caa05d9df62 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Cast01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Cast01.java
@@ -32,7 +32,7 @@
  */
 public class VN_Cast01 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         int field = 9;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Cast02.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Cast02.java
index 077ac36d1527..08ea2ccaa129 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Cast02.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Cast02.java
@@ -32,7 +32,7 @@
  */
 public class VN_Cast02 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         int field = 9;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Field01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Field01.java
index b157f8f0b1cf..64ab6e59d60c 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Field01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Field01.java
@@ -32,7 +32,7 @@
  */
 public class VN_Field01 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         int field = 9;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Field02.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Field02.java
index 3c8bb73a5371..853cf09e65d3 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Field02.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/optimize/VN_Field02.java
@@ -32,7 +32,7 @@
  */
 public class VN_Field02 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         int field = 9;
     }
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_get03.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_get03.java
index 3901fc70f773..340cf8f563c4 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_get03.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_get03.java
@@ -57,7 +57,7 @@ public class Field_get03 extends JTTTest {
         }
     }
 
-    private static class TestClass {
+    private static final class TestClass {
         public final byte byteField = 11;
         public final short shortField = 12;
         public final char charField = 13;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_get04.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_get04.java
index 2e82317b707c..9fb76da0ada7 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_get04.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_get04.java
@@ -31,7 +31,7 @@
  */
 public class Field_get04 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         public final byte byteField = 11;
         public final short shortField = 12;
         public final char charField = 13;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_set02.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_set02.java
index 09ea48607fb7..f8f26c7b7362 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_set02.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_set02.java
@@ -33,7 +33,7 @@
  */
 public class Field_set02 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         public byte byteField;
         public short shortField;
         public char charField;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_set03.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_set03.java
index 79e9e6dd1eaf..dcb7bcfc98d8 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_set03.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/reflect/Field_set03.java
@@ -31,7 +31,7 @@
  */
 public class Field_set03 extends JTTTest {
 
-    private static class TestClass {
+    private static final class TestClass {
         public byte byteField;
         public short shortField;
         public char charField;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Monitor_contended01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Monitor_contended01.java
index 755a11aeb517..260629ee709f 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Monitor_contended01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Monitor_contended01.java
@@ -35,7 +35,7 @@ public final class Monitor_contended01 extends JTTTest {
 
     @Rule public TestRule timeout = createTimeoutSeconds(20);
 
-    private static class TestClass implements Runnable {
+    private static final class TestClass implements Runnable {
         boolean started = false;
         boolean acquired = false;
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait01.java
index 39b1904b8f7f..c5578d1cbe50 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait01.java
@@ -35,7 +35,7 @@ public class Object_wait01 extends JTTTest {
 
     @Rule public TestRule timeout = createTimeoutSeconds(20);
 
-    private static class TestClass implements Runnable {
+    private static final class TestClass implements Runnable {
         @Override
         public void run() {
             int i = 0;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait02.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait02.java
index 6ccdf222af4b..9a2b9715a048 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait02.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait02.java
@@ -35,7 +35,7 @@ public class Object_wait02 extends JTTTest {
 
     @Rule public TestRule timeout = createTimeoutSeconds(20);
 
-    private static class TestClass implements Runnable {
+    private static final class TestClass implements Runnable {
         @Override
         public void run() {
             try {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait03.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait03.java
index 17be435b6c9c..063e987d3af4 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait03.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait03.java
@@ -50,7 +50,7 @@ public class Object_wait03 extends JTTTest {
 
     @Rule public TestRule timeout = createTimeoutMillis(TIMEOUT_MS);
 
-    private static class TestClass implements Runnable {
+    private static final class TestClass implements Runnable {
         @Override
         public void run() {
             try {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait04.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait04.java
index e0dc85427507..09d37a8444a8 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait04.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Object_wait04.java
@@ -35,7 +35,7 @@ public class Object_wait04 extends JTTTest {
 
     @Rule public TestRule timeout = createTimeoutSeconds(20);
 
-    private static class TestClass implements Runnable {
+    private static final class TestClass implements Runnable {
         @Override
         public void run() {
             try {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/ThreadLocal03.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/ThreadLocal03.java
index 3d47d7c3af91..7a716281dda7 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/ThreadLocal03.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/ThreadLocal03.java
@@ -49,7 +49,7 @@ public static int test(int i) {
         return sum;
     }
 
-    private static class TThread extends Thread {
+    private static final class TThread extends Thread {
 
         int input;
         int output;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_isInterrupted02.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_isInterrupted02.java
index 3ff8d9fbdb75..264c411d68cc 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_isInterrupted02.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_isInterrupted02.java
@@ -67,7 +67,7 @@ public static boolean test(int i, int time) throws InterruptedException {
         return thread.interrupted;
     }
 
-    private static class Thread extends java.lang.Thread {
+    private static final class Thread extends java.lang.Thread {
 
         private boolean interrupted;
         private boolean sentInterrupt;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_isInterrupted03.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_isInterrupted03.java
index 3197f1206162..436385fb2a84 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_isInterrupted03.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_isInterrupted03.java
@@ -50,7 +50,7 @@ public static boolean test() throws InterruptedException {
         return result;
     }
 
-    private static class Thread1 extends java.lang.Thread {
+    private static final class Thread1 extends java.lang.Thread {
 
         private boolean interrupted = false;
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_join01.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_join01.java
index 1652081e2897..90cbfc44fda8 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_join01.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_join01.java
@@ -35,7 +35,7 @@ public class Thread_join01 extends JTTTest {
 
     @Rule public TestRule timeout = createTimeoutSeconds(20);
 
-    private static class TestClass implements Runnable {
+    private static final class TestClass implements Runnable {
         @Override
         public void run() {
             cont = false;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_join02.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_join02.java
index 3604cc59fea5..12737228b2ca 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_join02.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_join02.java
@@ -38,7 +38,7 @@ public class Thread_join02 extends JTTTest {
 
     @Rule public TestRule timeout = createTimeoutSeconds(20);
 
-    private static class TestClass implements Runnable {
+    private static final class TestClass implements Runnable {
         @Override
         public void run() {
             try {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_join03.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_join03.java
index 73a4c8de4389..529299a88ade 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_join03.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_join03.java
@@ -38,7 +38,7 @@ public class Thread_join03 extends JTTTest {
 
     @Rule public TestRule timeout = createTimeoutSeconds(20);
 
-    private static class TestClass implements Runnable {
+    private static final class TestClass implements Runnable {
         @Override
         public void run() {
             cont = false;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_new02.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_new02.java
index d6a506df900d..e08ed559082c 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_new02.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/jtt/threads/Thread_new02.java
@@ -31,7 +31,7 @@
 
 public class Thread_new02 extends JTTTest {
 
-    private static class TestClass implements Runnable {
+    private static final class TestClass implements Runnable {
         @Override
         public void run() {
             // do nothing.
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/lir/jtt/ConstantStackCastTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/lir/jtt/ConstantStackCastTest.java
index 5bf8f6f5b70c..024f760b203f 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/lir/jtt/ConstantStackCastTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/lir/jtt/ConstantStackCastTest.java
@@ -57,7 +57,7 @@ public void setup() {
         stackCopyByte.srcKind = LIRKind.fromJavaKind(getBackend().getTarget().arch, JavaKind.Byte);
     }
 
-    private static class LoadConstantStackSpec extends LIRTestSpecification {
+    private static final class LoadConstantStackSpec extends LIRTestSpecification {
         LIRKind dstKind;
         LIRKind srcKind;
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/replacements/test/CompiledNullPointerExceptionTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/replacements/test/CompiledNullPointerExceptionTest.java
index 227e836c9413..ca88c912ad4e 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/replacements/test/CompiledNullPointerExceptionTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/replacements/test/CompiledNullPointerExceptionTest.java
@@ -73,7 +73,7 @@ protected StructuredGraph parse(Builder builder, PhaseSuite<HighTierContext> gra
         return graph;
     }
 
-    private class TestClass {
+    private final class TestClass {
 
         @Override
         public String toString() {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/replacements/test/DerivedOopTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/replacements/test/DerivedOopTest.java
index a4f2a151f428..89c79decf7f2 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/replacements/test/DerivedOopTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/replacements/test/DerivedOopTest.java
@@ -52,7 +52,7 @@
  */
 public class DerivedOopTest extends ReplacementsTest implements Snippets {
 
-    private static class Pointers {
+    private static final class Pointers {
         public long basePointer;
         public long internalPointer;
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/replacements/test/DynamicNewArrayTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/replacements/test/DynamicNewArrayTest.java
index 6f103add51c0..90d7fd08cc1d 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/replacements/test/DynamicNewArrayTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/replacements/test/DynamicNewArrayTest.java
@@ -37,7 +37,7 @@
  */
 public class DynamicNewArrayTest extends GraalCompilerTest {
 
-    private class Element {
+    private final class Element {
     }
 
     @Test
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/AssumedValuePartialEvaluationTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/AssumedValuePartialEvaluationTest.java
index d717dad4fb47..4532c3871fda 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/AssumedValuePartialEvaluationTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/AssumedValuePartialEvaluationTest.java
@@ -115,7 +115,7 @@ public int execute(VirtualFrame frame) {
         }
     }
 
-    private static class ReadDynamicAssumedValueNode extends AbstractTestNode {
+    private static final class ReadDynamicAssumedValueNode extends AbstractTestNode {
 
         @Override
         public int execute(VirtualFrame frame) {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/BytecodeDSLCompilationTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/BytecodeDSLCompilationTest.java
index 47acbe5f53c5..34a5923a29c7 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/BytecodeDSLCompilationTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/BytecodeDSLCompilationTest.java
@@ -961,7 +961,7 @@ protected void onCreate(Env env) {
         }
     }
 
-    private static class Counter {
+    private static final class Counter {
         private int count = 0;
 
         public int get() {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/ConditionAnchoringTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/ConditionAnchoringTest.java
index 6cc494b56839..95c264403e5a 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/ConditionAnchoringTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/ConditionAnchoringTest.java
@@ -76,7 +76,7 @@ public class ConditionAnchoringTest extends GraalCompilerTest {
         offset = fieldOffset;
     }
 
-    private static class CheckedObject {
+    private static final class CheckedObject {
         int id;
         int iid;
         @SuppressWarnings("unused") int field;
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/JFRPartialEvaluationTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/JFRPartialEvaluationTest.java
index d57bf7dee456..d0f6888119db 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/JFRPartialEvaluationTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/JFRPartialEvaluationTest.java
@@ -178,7 +178,7 @@ public int execute(VirtualFrame frame) {
     }
 
     @Name("test.JFRPartialEvaluationTestEvent")
-    private static class TestEvent extends Event {
+    private static final class TestEvent extends Event {
     }
 
     private static MethodCallTargetNode findInvoke(StructuredGraph graph, ResolvedJavaMethod expectedMethod) {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/LanguageContextFreedTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/LanguageContextFreedTest.java
index dab12531497d..65eec4727dbb 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/LanguageContextFreedTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/LanguageContextFreedTest.java
@@ -222,7 +222,7 @@ protected ContextReference<LanguageContext> getContextReference0() {
 
     }
 
-    private static class ContextLocalValue {
+    private static final class ContextLocalValue {
     }
 
 }
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/OptimizedOSRLoopNodeTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/OptimizedOSRLoopNodeTest.java
index 749eb5cd6018..050aa1838fe1 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/OptimizedOSRLoopNodeTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/OptimizedOSRLoopNodeTest.java
@@ -487,7 +487,7 @@ public void testCustomLoopContributingToOSR4(OSRLoopFactory factory) {
         assertNotCompiled(rootNode.getOSRTarget());
     }
 
-    private static class CustomInnerLoopRepeatingNode extends TestRepeatingNode {
+    private static final class CustomInnerLoopRepeatingNode extends TestRepeatingNode {
 
         @Override
         public boolean executeRepeating(VirtualFrame frame) {
@@ -611,7 +611,7 @@ public Void visitFrame(FrameInstance frameInstance) {
 
     }
 
-    private static class TestOSRStackTraceFromAbove extends TestOSRStackTrace {
+    private static final class TestOSRStackTraceFromAbove extends TestOSRStackTrace {
 
         @Child DirectCallNode callNode;
 
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/PerformanceWarningTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/PerformanceWarningTest.java
index 5124ceae1bff..585fe6793506 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/PerformanceWarningTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/PerformanceWarningTest.java
@@ -174,7 +174,7 @@ private interface SingleImplementedInterface {
         void doVirtual();
     }
 
-    private static class VirtualObject1 implements Interface {
+    private static final class VirtualObject1 implements Interface {
         @Override
         public void doVirtual() {
         }
@@ -184,7 +184,7 @@ public void doBoundaryVirtual() {
         }
     }
 
-    private static class VirtualObject2 implements Interface {
+    private static final class VirtualObject2 implements Interface {
         @Override
         public void doVirtual() {
         }
@@ -200,7 +200,7 @@ public void doVirtual() {
         }
     }
 
-    private static class SubClass extends SingleImplementorClass {
+    private static final class SubClass extends SingleImplementorClass {
     }
 
     private static class L1 {
@@ -227,10 +227,10 @@ private static class L7 extends L6 {
     private static class L8 extends L7 {
     }
 
-    private static class L9a extends L8 {
+    private static final class L9a extends L8 {
     }
 
-    private static class L9b extends L8 {
+    private static final class L9b extends L8 {
     }
 
     private abstract static class TestRootNode extends RootNode {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/TransferToInterpreterTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/TransferToInterpreterTest.java
index f111e5fd5ce4..84b491875423 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/TransferToInterpreterTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/TransferToInterpreterTest.java
@@ -61,7 +61,7 @@ public void test() {
         Assert.assertFalse(target.isValid());
     }
 
-    private static class TestTruffleCompilationTask implements TruffleCompilationTask {
+    private static final class TestTruffleCompilationTask implements TruffleCompilationTask {
 
         @Override
         public boolean isCancelled() {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/libgraal/JNIExceptionWrapperTest.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/libgraal/JNIExceptionWrapperTest.java
index dec6396960d0..af7d3104de9c 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/libgraal/JNIExceptionWrapperTest.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/libgraal/JNIExceptionWrapperTest.java
@@ -101,7 +101,7 @@ public void onGraalTierFinished(TruffleCompilable compilable, GraphInfo graph) {
         }
     }
 
-    private static class TestTruffleCompilationTask implements TruffleCompilationTask {
+    private static final class TestTruffleCompilationTask implements TruffleCompilationTask {
 
         @Override
         public boolean isCancelled() {
diff --git a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/nodes/NeverPartOfCompilationTestNode.java b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/nodes/NeverPartOfCompilationTestNode.java
index 941995b74d66..d531ed94efb5 100644
--- a/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/nodes/NeverPartOfCompilationTestNode.java
+++ b/compiler/src/jdk.graal.compiler.test/src/jdk/graal/compiler/truffle/test/nodes/NeverPartOfCompilationTestNode.java
@@ -32,7 +32,7 @@ public class NeverPartOfCompilationTestNode extends AbstractTestNode {
     @Child private AbstractTestNode left;
     private final int value;
 
-    private static class ValueContainer {
+    private static final class ValueContainer {
         int value;
     }
 
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/asm/amd64/AMD64BaseAssembler.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/asm/amd64/AMD64BaseAssembler.java
index bcd0073cceca..f9506a175e3b 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/asm/amd64/AMD64BaseAssembler.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/asm/amd64/AMD64BaseAssembler.java
@@ -351,7 +351,7 @@ protected static int encode(Register r) {
     /**
      * Constants for X86 prefix bytes.
      */
-    private static class Prefix {
+    private static final class Prefix {
         private static final int REX = 0x40;
         private static final int REXB = 0x41;
         private static final int REXX = 0x42;
@@ -828,7 +828,7 @@ private interface SIMDEncoder {
 
     }
 
-    private class SSEEncoderImpl implements SIMDEncoder {
+    private final class SSEEncoderImpl implements SIMDEncoder {
 
         @Override
         public void simdPrefix(Register xreg, Register nds, AMD64Address adr, int sizePrefix, int opcodeEscapePrefix, boolean isRexW) {
@@ -890,7 +890,7 @@ private VEXPrefixConfig() {
         }
     }
 
-    private class VEXEncoderImpl implements SIMDEncoder {
+    private final class VEXEncoderImpl implements SIMDEncoder {
 
         private int sizePrefixToPP(int sizePrefix) {
             switch (sizePrefix) {
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/core/common/calc/Condition.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/core/common/calc/Condition.java
index b5a20152a000..1c187c2d380e 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/core/common/calc/Condition.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/core/common/calc/Condition.java
@@ -387,6 +387,7 @@ public TriState foldCondition(Stamp compareStamp, Constant lt, Constant rt, Cons
      *         false
      */
     public boolean foldCondition(PrimitiveConstant lp, PrimitiveConstant rp, boolean unorderedIsTrue) {
+        // Checkstyle: stop FallThrough
         switch (lp.getJavaKind()) {
             case Boolean:
             case Byte:
@@ -497,6 +498,7 @@ public boolean foldCondition(PrimitiveConstant lp, PrimitiveConstant rp, boolean
             default:
                 throw new GraalError("expected value kind %s while folding condition: %s", lp.getJavaKind(), this); // ExcludeFromJacocoGeneratedReport
         }
+        // Checkstyle: resume FallThrough
     }
 
     private static boolean in(Condition needle, Condition... haystack) {
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/core/common/type/FloatStamp.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/core/common/type/FloatStamp.java
index a18de1564ffa..01946ffe3db9 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/core/common/type/FloatStamp.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/core/common/type/FloatStamp.java
@@ -1680,7 +1680,7 @@ protected Stamp foldStampImpl(Stamp stamp) {
                     });
 
     // Use a separate class to avoid initialization cycles
-    private static class ConstantCache {
+    private static final class ConstantCache {
         private static final FloatStamp FLOAT_BOTTOM = new FloatStamp(Float.SIZE, Double.NEGATIVE_INFINITY, Double.POSITIVE_INFINITY, false);
         private static final FloatStamp DOUBLE_BOTTOM = new FloatStamp(Double.SIZE, Double.NEGATIVE_INFINITY, Double.POSITIVE_INFINITY, false);
         private static final FloatStamp FLOAT_TOP = new FloatStamp(Float.SIZE, Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY, true);
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/graphio/parsing/BinaryReader.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/graphio/parsing/BinaryReader.java
index 7b8881c43a1d..983d3c7beed3 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/graphio/parsing/BinaryReader.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/graphio/parsing/BinaryReader.java
@@ -103,7 +103,7 @@ public class BinaryReader implements GraphParser, ModelControl {
 
     private final Builder builder;
 
-    private static class ErrorReporter {
+    private static final class ErrorReporter {
         /**
          * Accumulates names of objects as they are parsed out of stream Used to report context for
          * irrecoverable errors which happen during reading BGV stream.
@@ -184,7 +184,7 @@ public void reportLoadingError(String message, Builder builder) {
         }
     }
 
-    private static class ContextStrings {
+    private static final class ContextStrings {
         private static String propertyGraph(Object s) {
             return String.format("Property %s graph", s);
         }
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/graphio/parsing/ModelBuilder.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/graphio/parsing/ModelBuilder.java
index c8df87e9c062..d539c0bdcea6 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/graphio/parsing/ModelBuilder.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/graphio/parsing/ModelBuilder.java
@@ -137,7 +137,7 @@ public int hashCode() {
         }
     }
 
-    private static class ErrorMessages {
+    private static final class ErrorMessages {
         public static String edgeStartNodeNotExists(String label, int node) {
             return String.format("Start node for edge %s does not exist: %d", label, node);
         }
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/graphio/parsing/model/Properties.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/graphio/parsing/model/Properties.java
index b25c90c1a26d..73e5a1ff50ea 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/graphio/parsing/model/Properties.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/graphio/parsing/model/Properties.java
@@ -208,7 +208,7 @@ <TSource extends Iterable<? extends TProp>, TProp> void addFrom(TSource source,
             }
         }
 
-        private class ArrayPropertiesIterator implements Iterator<Property<Object>> {
+        private final class ArrayPropertiesIterator implements Iterator<Property<Object>> {
             int index;
 
             @Override
@@ -575,7 +575,7 @@ public int hashCode() {
         }
     }
 
-    private static class PropertyCache {
+    private static final class PropertyCache {
         static final WeakHashMap</* Shared */ Properties, WeakReference<SharedProperties>> immutableCache = new WeakHashMap<>();
 
         static synchronized SharedProperties intern(Properties properties) {
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/hightiercodegen/reconstruction/stackifier/blocks/LabeledBlockGeneration.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/hightiercodegen/reconstruction/stackifier/blocks/LabeledBlockGeneration.java
index 136db5928690..f84d4a5be67d 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/hightiercodegen/reconstruction/stackifier/blocks/LabeledBlockGeneration.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/hightiercodegen/reconstruction/stackifier/blocks/LabeledBlockGeneration.java
@@ -531,7 +531,7 @@ private void addToMaps(LabeledBlock labeledBLock) {
     /**
      * Generates {@link LabeledBlock}s with unique labels.
      */
-    private static class LabeledBlockGenerator {
+    private static final class LabeledBlockGenerator {
 
         private int currentId = 0;
 
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/hotspot/stubs/Stub.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/hotspot/stubs/Stub.java
index 76bf4fd14ef2..ea38d909d002 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/hotspot/stubs/Stub.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/hotspot/stubs/Stub.java
@@ -290,7 +290,7 @@ protected void checkSafeDataReference(DataPatch data) {
         assert !(data.reference instanceof ConstantReference) : this + " cannot have embedded object or metadata constant: " + data.reference;
     }
 
-    private static class EmptyHighTier extends BasePhase<HighTierContext> {
+    private static final class EmptyHighTier extends BasePhase<HighTierContext> {
         @Override
         public Optional<NotApplicable> notApplicableTo(GraphState graphState) {
             return ALWAYS_APPLICABLE;
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/lir/aarch64/AArch64ArrayIndexOfOp.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/lir/aarch64/AArch64ArrayIndexOfOp.java
index 9dc63915eaa6..a0e06bdbdc37 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/lir/aarch64/AArch64ArrayIndexOfOp.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/lir/aarch64/AArch64ArrayIndexOfOp.java
@@ -108,6 +108,7 @@ public AArch64ArrayIndexOfOp(Stride stride, ArrayIndexOfVariant variant, LIRGene
     }
 
     private static int getNumberOfRequiredVectorRegisters(ArrayIndexOfVariant variant, Stride stride, int nValues) {
+        // Checkstyle: stop FallThrough
         switch (variant) {
             case MatchAny:
                 return nValues + (nValues > 1 ? 6 : 3);
@@ -132,6 +133,7 @@ private static int getNumberOfRequiredVectorRegisters(ArrayIndexOfVariant varian
             default:
                 throw GraalError.shouldNotReachHereUnexpectedValue(variant); // ExcludeFromJacocoGeneratedReport
         }
+        // Checkstyle: resume FallThrough
     }
 
     private void emitScalarCode(AArch64MacroAssembler masm, Register baseAddress, Register searchLength) {
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/lir/amd64/AMD64ComplexVectorOp.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/lir/amd64/AMD64ComplexVectorOp.java
index 25cbb70f60e3..f51a09a3144f 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/lir/amd64/AMD64ComplexVectorOp.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/lir/amd64/AMD64ComplexVectorOp.java
@@ -88,6 +88,7 @@ private static boolean isXMMOrGreater(AVXSize size) {
     }
 
     protected AMD64Kind getVectorKind(JavaKind valueKind) {
+        // Checkstyle: stop FallThrough
         switch (vectorSize) {
             case XMM:
                 switch (valueKind) {
@@ -143,9 +144,11 @@ protected AMD64Kind getVectorKind(JavaKind valueKind) {
             default:
                 throw GraalError.shouldNotReachHere("Unsupported vector size.");
         }
+        // Checkstyle: resume FallThrough
     }
 
     protected AMD64Kind getVectorKind(Stride stride) {
+        // Checkstyle: stop FallThrough
         switch (vectorSize) {
             case XMM:
                 switch (stride) {
@@ -189,6 +192,7 @@ protected AMD64Kind getVectorKind(Stride stride) {
             default:
                 throw GraalError.shouldNotReachHere("Unsupported vector size."); // ExcludeFromJacocoGeneratedReport
         }
+        // Checkstyle: resume FallThrough
     }
 
     protected Value[] allocateTempRegisters(LIRGeneratorTool tool, AMD64Kind kind, int n) {
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/lir/amd64/phases/StackMoveOptimizationPhase.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/lir/amd64/phases/StackMoveOptimizationPhase.java
index 94ebfdf0ffdc..23d808a6e64d 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/lir/amd64/phases/StackMoveOptimizationPhase.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/lir/amd64/phases/StackMoveOptimizationPhase.java
@@ -76,7 +76,7 @@ protected void run(TargetDescription target, LIRGenerationResult lirGenRes, Post
         }
     }
 
-    private static class Closure {
+    private static final class Closure {
         private static final int NONE = -1;
 
         private int begin = NONE;
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/debug/NeverStripMineNode.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/debug/NeverStripMineNode.java
index cc0098c8c0e3..7fd106197d01 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/debug/NeverStripMineNode.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/debug/NeverStripMineNode.java
@@ -42,7 +42,7 @@ public final class NeverStripMineNode extends FixedWithNextNode implements LIRLo
 
     public static final NodeClass<NeverStripMineNode> TYPE = NodeClass.create(NeverStripMineNode.class);
 
-    private static class Unique {
+    private static final class Unique {
     }
 
     protected Unique unique;
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/debug/NeverWriteSinkNode.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/debug/NeverWriteSinkNode.java
index 53aab793a2ec..0be84e614146 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/debug/NeverWriteSinkNode.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/debug/NeverWriteSinkNode.java
@@ -42,7 +42,7 @@ public final class NeverWriteSinkNode extends FixedWithNextNode implements LIRLo
 
     public static final NodeClass<NeverWriteSinkNode> TYPE = NodeClass.create(NeverWriteSinkNode.class);
 
-    private static class Unique {
+    private static final class Unique {
     }
 
     protected Unique unique;
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/graphbuilderconf/InvocationPlugins.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/graphbuilderconf/InvocationPlugins.java
index 3faae8f9c4a9..5ded5f9bcc23 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/graphbuilderconf/InvocationPlugins.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/nodes/graphbuilderconf/InvocationPlugins.java
@@ -1057,7 +1057,7 @@ public boolean maybePrintIntrinsics(OptionValues options) {
     /**
      * Code only used in assertions. Putting this in a separate class reduces class load time.
      */
-    private static class Checks {
+    private static final class Checks {
         private static final int MAX_ARITY = 13;
         /**
          * The set of all {@link InvocationPlugin#apply} method signatures.
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/common/FrameStateAssignmentPhase.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/common/FrameStateAssignmentPhase.java
index 46ed6ac580fe..8b7af0388d00 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/common/FrameStateAssignmentPhase.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/common/FrameStateAssignmentPhase.java
@@ -61,7 +61,7 @@
  */
 public class FrameStateAssignmentPhase extends Phase {
 
-    private static class FrameStateAssignmentClosure extends ReentrantNodeIterator.NodeIteratorClosure<FrameState> {
+    private static final class FrameStateAssignmentClosure extends ReentrantNodeIterator.NodeIteratorClosure<FrameState> {
 
         @Override
         protected FrameState processNode(FixedNode node, FrameState previousState) {
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/common/InitMemoryVerificationPhase.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/common/InitMemoryVerificationPhase.java
index 38320626146b..8a5adeb68569 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/common/InitMemoryVerificationPhase.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/common/InitMemoryVerificationPhase.java
@@ -85,7 +85,7 @@ public Optional<NotApplicable> notApplicableTo(GraphState graphState) {
      * {@link MemoryKill} writing to, we simply count the number of memory kills that are "live"
      * (not protected by a barrier) at any point in the control flow graph..
      */
-    private static class InitBarrierVerificationClosure extends ReentrantNodeIterator.NodeIteratorClosure<Integer> {
+    private static final class InitBarrierVerificationClosure extends ReentrantNodeIterator.NodeIteratorClosure<Integer> {
         @Override
         protected Integer processNode(FixedNode node, Integer kills) {
             int liveKills = kills;
@@ -131,7 +131,7 @@ protected EconomicMap<LoopExitNode, Integer> processLoop(LoopBeginNode loop, Int
      * Verifies that all {@link AbstractNewObjectNode AbstractNewObjectNodes} are published by a
      * {@link PublishWritesNode}.
      */
-    private static class AllocPublishVerificationClosure extends ReentrantNodeIterator.NodeIteratorClosure<EconomicSet<AbstractNewObjectNode>> {
+    private static final class AllocPublishVerificationClosure extends ReentrantNodeIterator.NodeIteratorClosure<EconomicSet<AbstractNewObjectNode>> {
         private static void processAlloc(AbstractNewObjectNode allocation, EconomicSet<AbstractNewObjectNode> unpublished) {
             if (allocation.emitMemoryBarrier() && allocation.fillContents()) {
                 // Allocation was not lowered from a CommitAllocationNode, can ignore
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/schedule/SchedulePhase.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/schedule/SchedulePhase.java
index 4c0d1c40db43..34c3e7c00a0b 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/schedule/SchedulePhase.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/phases/schedule/SchedulePhase.java
@@ -1126,7 +1126,7 @@ private static void processStack(Node first, MicroBlock startBlock, NodeMap<Micr
             }
         }
 
-        private static class GuardOrder {
+        private static final class GuardOrder {
             /**
              * After an earliest schedule, this will re-sort guards to honor their
              * {@linkplain StaticDeoptimizingNode#computePriority() priority}.
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/printer/GraalDebugHandlersFactory.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/printer/GraalDebugHandlersFactory.java
index 6c026c18803b..0b2d6a608d26 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/printer/GraalDebugHandlersFactory.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/printer/GraalDebugHandlersFactory.java
@@ -72,7 +72,7 @@ public List<DebugHandler> createHandlers(OptionValues options) {
         return handlers;
     }
 
-    private static class NodeDumper implements DebugDumpHandler {
+    private static final class NodeDumper implements DebugDumpHandler {
         @Override
         public void dump(Object object, DebugContext debug, boolean forced, String format, Object... arguments) {
             if (debug.isLogEnabled()) {
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/replacements/nodes/ArrayIndexOfForeignCalls.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/replacements/nodes/ArrayIndexOfForeignCalls.java
index f56769e8dafe..19cbfe9cdb9d 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/replacements/nodes/ArrayIndexOfForeignCalls.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/replacements/nodes/ArrayIndexOfForeignCalls.java
@@ -159,6 +159,7 @@ private static LIRGeneratorTool.ArrayIndexOfVariant getVariant(ForeignCallDescri
     public static ForeignCallDescriptor getStub(ArrayIndexOfNode indexOfNode) {
         Stride stride = indexOfNode.getStride();
         int valueCount = indexOfNode.getNumberOfValues();
+        // Checkstyle: stop FallThrough
         switch (indexOfNode.getVariant()) {
             case MatchAny:
                 int index = (4 * stride.log2) + (valueCount - 1);
@@ -221,5 +222,6 @@ public static ForeignCallDescriptor getStub(ArrayIndexOfNode indexOfNode) {
             default:
                 throw GraalError.shouldNotReachHereUnexpectedValue(indexOfNode.getVariant()); // ExcludeFromJacocoGeneratedReport
         }
+        // Checkstyle: resume FallThrough
     }
 }
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/truffle/TruffleCompilerImpl.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/truffle/TruffleCompilerImpl.java
index 773c6d51e1b4..a227137e5f28 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/truffle/TruffleCompilerImpl.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/truffle/TruffleCompilerImpl.java
@@ -902,7 +902,7 @@ public final SnippetReflectionProvider getSnippetReflection() {
         return config.snippetReflection();
     }
 
-    private class TrufflePostCodeInstallationTaskFactory extends Backend.CodeInstallationTaskFactory {
+    private final class TrufflePostCodeInstallationTaskFactory extends Backend.CodeInstallationTaskFactory {
 
         @Override
         public Backend.CodeInstallationTask create() {
diff --git a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/virtual/phases/ea/PartialEscapeBlockState.java b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/virtual/phases/ea/PartialEscapeBlockState.java
index 9eaf47a022a8..4e0380b0e0ec 100644
--- a/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/virtual/phases/ea/PartialEscapeBlockState.java
+++ b/compiler/src/jdk.graal.compiler/src/jdk/graal/compiler/virtual/phases/ea/PartialEscapeBlockState.java
@@ -74,7 +74,7 @@ public boolean contains(VirtualObjectNode value) {
         return false;
     }
 
-    private static class RefCount {
+    private static final class RefCount {
         private int refCount = 1;
     }
 
diff --git a/compiler/src/org.graalvm.profdiff.test/src/org/graalvm/profdiff/test/DeltaTreeTest.java b/compiler/src/org.graalvm.profdiff.test/src/org/graalvm/profdiff/test/DeltaTreeTest.java
index 69c85876d61a..d8e4754d3828 100644
--- a/compiler/src/org.graalvm.profdiff.test/src/org/graalvm/profdiff/test/DeltaTreeTest.java
+++ b/compiler/src/org.graalvm.profdiff.test/src/org/graalvm/profdiff/test/DeltaTreeTest.java
@@ -68,7 +68,7 @@ protected MockTreeNode() {
         }
     }
 
-    private static class MockInfoNode extends MockTreeNode {
+    private static final class MockInfoNode extends MockTreeNode {
         @Override
         public boolean isInfoNode() {
             return true;
diff --git a/compiler/src/org.graalvm.profdiff.test/src/org/graalvm/profdiff/test/TreeMatcherTest.java b/compiler/src/org.graalvm.profdiff.test/src/org/graalvm/profdiff/test/TreeMatcherTest.java
index bb5c8f07504b..78271a651e87 100644
--- a/compiler/src/org.graalvm.profdiff.test/src/org/graalvm/profdiff/test/TreeMatcherTest.java
+++ b/compiler/src/org.graalvm.profdiff.test/src/org/graalvm/profdiff/test/TreeMatcherTest.java
@@ -39,7 +39,7 @@ public class TreeMatcherTest {
      * The {@link OptimizationTreeEditPolicy} discourages relabelling, however, we still want to
      * test that the algorithm can find relabelling.
      */
-    private static class TestOptimizationTreeEditPolicy extends OptimizationTreeEditPolicy {
+    private static final class TestOptimizationTreeEditPolicy extends OptimizationTreeEditPolicy {
         @Override
         public long relabelCost(OptimizationTreeNode node1, OptimizationTreeNode node2) {
             assert node1 != node2;
diff --git a/compiler/src/org.graalvm.profdiff/src/org/graalvm/profdiff/parser/ExperimentParser.java b/compiler/src/org.graalvm.profdiff/src/org/graalvm/profdiff/parser/ExperimentParser.java
index 082520da3378..b015ab486c9c 100644
--- a/compiler/src/org.graalvm.profdiff/src/org/graalvm/profdiff/parser/ExperimentParser.java
+++ b/compiler/src/org.graalvm.profdiff/src/org/graalvm/profdiff/parser/ExperimentParser.java
@@ -138,7 +138,7 @@ private static final class PartialCompilationUnit {
     /**
      * A parsed proftool log.
      */
-    private static class ProftoolLog {
+    private static final class ProftoolLog {
         /**
          * The compilation kind of the parsed experiment (JIT/AOT).
          */
diff --git a/regex/mx.regex/suite.py b/regex/mx.regex/suite.py
index 6d10d646e0af..a2e14840e04f 100644
--- a/regex/mx.regex/suite.py
+++ b/regex/mx.regex/suite.py
@@ -92,7 +92,7 @@
         "jdk.unsupported", # sun.misc.Unsafe
       ],
       "annotationProcessors" : ["truffle:TRUFFLE_DSL_PROCESSOR"],
-      "checkstyleVersion" : "10.7.0",
+      "checkstyleVersion" : "10.21.0",
       "javaCompliance" : "17+",
       "workingSets" : "Truffle,Regex",
       "spotbugsIgnoresGenerated" : True,
diff --git a/sdk/mx.sdk/suite.py b/sdk/mx.sdk/suite.py
index 47c3323c02fa..9acea82d8953 100644
--- a/sdk/mx.sdk/suite.py
+++ b/sdk/mx.sdk/suite.py
@@ -39,7 +39,7 @@
 # SOFTWARE.
 #
 suite = {
-  "mxversion": "7.36.0",
+  "mxversion": "7.36.5",
   "name" : "sdk",
   "version" : "25.0.0",
   "release" : False,
@@ -409,7 +409,7 @@
       "dependencies" : [],
       "checkstyle" : "org.graalvm.word",
       "javaCompliance" : "11+",
-      "checkstyleVersion" : "10.7.0",
+      "checkstyleVersion" : "10.21.0",
       "workingSets" : "API,SDK",
     },
 
diff --git a/substratevm/mx.substratevm/suite.py b/substratevm/mx.substratevm/suite.py
index d527e1f0936b..c1076f561a03 100644
--- a/substratevm/mx.substratevm/suite.py
+++ b/substratevm/mx.substratevm/suite.py
@@ -347,7 +347,7 @@
                 ],
             },
             "javaCompliance" : "21+",
-            "checkstyleVersion" : "10.7.0",
+            "checkstyleVersion" : "10.21.0",
             "annotationProcessors": [
                 "compiler:GRAAL_PROCESSOR",
                 "SVM_PROCESSOR",
@@ -709,7 +709,7 @@
                 ],
             },
             "javaCompliance" : "21+",
-            "checkstyleVersion": "10.7.0",
+            "checkstyleVersion": "10.21.0",
             "annotationProcessors": [
                 "compiler:GRAAL_PROCESSOR",
                 "SVM_PROCESSOR",
@@ -1047,7 +1047,7 @@
                 ],
             },
             "checkstyle": "com.oracle.svm.test",
-            "checkstyleVersion" : "10.7.0",
+            "checkstyleVersion" : "10.21.0",
             "workingSets": "SVM",
             "annotationProcessors": [
                 "compiler:GRAAL_PROCESSOR",
diff --git a/substratevm/src/com.oracle.objectfile/src/com/oracle/objectfile/macho/MachOObjectFile.java b/substratevm/src/com.oracle.objectfile/src/com/oracle/objectfile/macho/MachOObjectFile.java
index 4ea5a2d02bd8..eb833b4c777e 100644
--- a/substratevm/src/com.oracle.objectfile/src/com/oracle/objectfile/macho/MachOObjectFile.java
+++ b/substratevm/src/com.oracle.objectfile/src/com/oracle/objectfile/macho/MachOObjectFile.java
@@ -381,7 +381,7 @@ public int getWrittenSize() {
 
     private LoadCommandList loadCommands = new LoadCommandList();
 
-    private class LoadCommandList implements Iterable<LoadCommand> {
+    private final class LoadCommandList implements Iterable<LoadCommand> {
 
         LinkEditSegment64Command linkEditCommand; // or null; if present, always comes last!
         List<LoadCommand> otherCommands = new ArrayList<>();
diff --git a/substratevm/src/com.oracle.svm.configure.test/src/com/oracle/svm/configure/test/conditionalconfig/ConfigurationGenerator.java b/substratevm/src/com.oracle.svm.configure.test/src/com/oracle/svm/configure/test/conditionalconfig/ConfigurationGenerator.java
index c96455a9164e..3ae40ae003b5 100644
--- a/substratevm/src/com.oracle.svm.configure.test/src/com/oracle/svm/configure/test/conditionalconfig/ConfigurationGenerator.java
+++ b/substratevm/src/com.oracle.svm.configure.test/src/com/oracle/svm/configure/test/conditionalconfig/ConfigurationGenerator.java
@@ -85,7 +85,7 @@ public static void runTest() {
     }
 
     @SuppressWarnings("unused")
-    private static class A {
+    private static final class A {
     }
 
     interface IA {
@@ -105,7 +105,7 @@ public static void runTest() {
         ParentB.doWork();
     }
 
-    private static class ParentA {
+    private static final class ParentA {
         static void doWork() {
             Util.doWork("PropagateToParent$ParentA", "PropagateToParentA.txt", IA.class);
         }
@@ -114,7 +114,7 @@ static void doWork() {
     interface IA {
     }
 
-    private static class ParentB {
+    private static final class ParentB {
         static void doWork() {
             Util.doWork("PropagateToParent$ParentB", "PropagateToParentB.txt", IB.class);
         }
@@ -123,7 +123,7 @@ static void doWork() {
     interface IB {
     }
 
-    private static class Util {
+    private static final class Util {
         static void doWork(String clazz, String resource, Class<?>... interfaceList) {
             ClassUtil.forName(clazz);
             ClassUtil.getResource(resource);
@@ -148,20 +148,20 @@ public static void runTest() {
         ParentB.doWork();
     }
 
-    private static class ParentA {
+    private static final class ParentA {
         static void doWork() {
             Util.doWork("PropagateButLeaveCommonConfiguration$ParentA", "PropagateToParentA.txt", IA.class);
         }
     }
 
-    private static class ParentB {
+    private static final class ParentB {
         static void doWork() {
             Util.doWork("PropagateButLeaveCommonConfiguration$ParentB", "PropagateToParentB.txt", IB.class);
         }
     }
 
     @SuppressWarnings("unused")
-    private static class C {
+    private static final class C {
     }
 
     interface IA {
@@ -173,7 +173,7 @@ interface IB {
     interface IC {
     }
 
-    private static class Util {
+    private static final class Util {
         static void doWork(String clazz, String resource, Class<?>... intefaceList) {
             ClassUtil.forName(clazz);
             ClassUtil.forName("PropagateButLeaveCommonConfiguration$C");
diff --git a/substratevm/src/com.oracle.svm.core.foreign/src/com/oracle/svm/core/foreign/AbiUtils.java b/substratevm/src/com.oracle.svm.core.foreign/src/com/oracle/svm/core/foreign/AbiUtils.java
index 4485b5781def..e9f8fd56e142 100644
--- a/substratevm/src/com.oracle.svm.core.foreign/src/com/oracle/svm/core/foreign/AbiUtils.java
+++ b/substratevm/src/com.oracle.svm.core.foreign/src/com/oracle/svm/core/foreign/AbiUtils.java
@@ -406,7 +406,7 @@ public List<ValueNode> apply(ValueNode parameter, Map<Extracted, ValueNode> extr
             }
         }
 
-        private final static class ExtractSingle extends Extract {
+        private static final class ExtractSingle extends Extract {
             private final Class<?> type;
 
             private ExtractSingle(Extracted as, Class<?> type) {
diff --git a/substratevm/src/com.oracle.svm.core.foreign/src/com/oracle/svm/core/foreign/Target_jdk_internal_foreign_abi_AbstractLinker.java b/substratevm/src/com.oracle.svm.core.foreign/src/com/oracle/svm/core/foreign/Target_jdk_internal_foreign_abi_AbstractLinker.java
index 4871809310e8..2505a994d9ce 100644
--- a/substratevm/src/com.oracle.svm.core.foreign/src/com/oracle/svm/core/foreign/Target_jdk_internal_foreign_abi_AbstractLinker.java
+++ b/substratevm/src/com.oracle.svm.core.foreign/src/com/oracle/svm/core/foreign/Target_jdk_internal_foreign_abi_AbstractLinker.java
@@ -111,4 +111,4 @@ UpcallStubFactory arrangeUpcall(MethodType targetType, FunctionDescriptor functi
 /*
  * GR-58659, GR-58660: add substitutions for LinuxAArch64Linker and MacOsAArch64Linker here once we
  * support them.
- */
\ No newline at end of file
+ */
diff --git a/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ChunkedImageHeapPartition.java b/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ChunkedImageHeapPartition.java
index 19292edb16a3..3f8232a42e97 100644
--- a/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ChunkedImageHeapPartition.java
+++ b/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ChunkedImageHeapPartition.java
@@ -225,7 +225,7 @@ public String toString() {
         return name;
     }
 
-    private static class SizeComparator implements Comparator<ImageHeapObject> {
+    private static final class SizeComparator implements Comparator<ImageHeapObject> {
         @Override
         public int compare(ImageHeapObject o1, ImageHeapObject o2) {
             return Long.signum(o1.getSize() - o2.getSize());
diff --git a/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/HeapImpl.java b/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/HeapImpl.java
index eb38e7dc100d..17f57d86f5a9 100644
--- a/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/HeapImpl.java
+++ b/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/HeapImpl.java
@@ -879,7 +879,7 @@ private static void writeToEachChunk(HeapChunk.Header<?> firstChunk, HeapChunk.H
         }
     }
 
-    private static class DumpHeapSettingsAndStatistics extends DiagnosticThunk {
+    private static final class DumpHeapSettingsAndStatistics extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 1;
@@ -907,7 +907,7 @@ public void printDiagnostics(Log log, ErrorContext context, int maxDiagnosticLev
         }
     }
 
-    private static class DumpHeapUsage extends DiagnosticThunk {
+    private static final class DumpHeapUsage extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 1;
@@ -922,7 +922,7 @@ public void printDiagnostics(Log log, ErrorContext context, int maxDiagnosticLev
         }
     }
 
-    private static class DumpChunkInformation extends DiagnosticThunk {
+    private static final class DumpChunkInformation extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 1;
diff --git a/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/graal/GenScavengeAllocationSnippets.java b/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/graal/GenScavengeAllocationSnippets.java
index 4c80a282573b..fe0bd294fd84 100644
--- a/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/graal/GenScavengeAllocationSnippets.java
+++ b/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/graal/GenScavengeAllocationSnippets.java
@@ -147,7 +147,7 @@ public void registerLowering(Map<Class<? extends Node>, NodeLoweringProvider<?>>
             }
         }
 
-        private class FormatObjectLowering implements NodeLoweringProvider<FormatObjectNode> {
+        private final class FormatObjectLowering implements NodeLoweringProvider<FormatObjectNode> {
             @Override
             public void lower(FormatObjectNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -165,7 +165,7 @@ public void lower(FormatObjectNode node, LoweringTool tool) {
             }
         }
 
-        private class FormatArrayLowering implements NodeLoweringProvider<FormatArrayNode> {
+        private final class FormatArrayLowering implements NodeLoweringProvider<FormatArrayNode> {
             @Override
             public void lower(FormatArrayNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -187,7 +187,7 @@ public void lower(FormatArrayNode node, LoweringTool tool) {
             }
         }
 
-        private class FormatStoredContinuationLowering implements NodeLoweringProvider<FormatStoredContinuationNode> {
+        private final class FormatStoredContinuationLowering implements NodeLoweringProvider<FormatStoredContinuationNode> {
             @Override
             public void lower(FormatStoredContinuationNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -207,7 +207,7 @@ public void lower(FormatStoredContinuationNode node, LoweringTool tool) {
             }
         }
 
-        private class FormatPodLowering implements NodeLoweringProvider<FormatPodNode> {
+        private final class FormatPodLowering implements NodeLoweringProvider<FormatPodNode> {
             @Override
             public void lower(FormatPodNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
diff --git a/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/remset/CardTable.java b/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/remset/CardTable.java
index 4c2159fe7459..48eaa6c642f9 100644
--- a/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/remset/CardTable.java
+++ b/substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/remset/CardTable.java
@@ -220,7 +220,7 @@ private static boolean verifyReference(Object parentObject, Pointer cardTableSta
         return true;
     }
 
-    private static class CardTableVerificationVisitor implements ObjectReferenceVisitor {
+    private static final class CardTableVerificationVisitor implements ObjectReferenceVisitor {
         private Object parentObject;
         private Pointer cardTableStart;
         private Pointer objectsStart;
diff --git a/substratevm/src/com.oracle.svm.core.graal.amd64/src/com/oracle/svm/core/graal/amd64/AMD64CalleeSavedRegisters.java b/substratevm/src/com.oracle.svm.core.graal.amd64/src/com/oracle/svm/core/graal/amd64/AMD64CalleeSavedRegisters.java
index dd727e79a35c..2effa91e82b0 100644
--- a/substratevm/src/com.oracle.svm.core.graal.amd64/src/com/oracle/svm/core/graal/amd64/AMD64CalleeSavedRegisters.java
+++ b/substratevm/src/com.oracle.svm.core.graal.amd64/src/com/oracle/svm/core/graal/amd64/AMD64CalleeSavedRegisters.java
@@ -262,7 +262,7 @@ private enum Mode {
      * "Control-flow exception" to indicate that a CPU feature is statically available and no
      * further dynamic feature checks are needed.
      */
-    private static class StaticFeatureException extends Exception {
+    private static final class StaticFeatureException extends Exception {
         static final long serialVersionUID = -1;
     }
 
diff --git a/substratevm/src/com.oracle.svm.core.graal.llvm/src/com/oracle/svm/core/graal/llvm/LLVMNativeImageCodeCache.java b/substratevm/src/com.oracle.svm.core.graal.llvm/src/com/oracle/svm/core/graal/llvm/LLVMNativeImageCodeCache.java
index f0a6e6d6994a..1cedfffa2785 100644
--- a/substratevm/src/com.oracle.svm.core.graal.llvm/src/com/oracle/svm/core/graal/llvm/LLVMNativeImageCodeCache.java
+++ b/substratevm/src/com.oracle.svm.core.graal.llvm/src/com/oracle/svm/core/graal/llvm/LLVMNativeImageCodeCache.java
@@ -374,7 +374,7 @@ public interface StackMapDumper {
         void close();
     }
 
-    private class EnabledStackMapDumper implements StackMapDumper {
+    private final class EnabledStackMapDumper implements StackMapDumper {
         private final FileWriter stackMapDump;
 
         {
@@ -454,7 +454,7 @@ private void dump(String str) {
         }
     }
 
-    private static class DisabledStackMapDumper implements StackMapDumper {
+    private static final class DisabledStackMapDumper implements StackMapDumper {
         @Override
         public void dumpOffsets(LLVMTextSectionInfo textSectionInfo) {
         }
diff --git a/substratevm/src/com.oracle.svm.core.graal.llvm/src/com/oracle/svm/core/graal/llvm/runtime/LLVMExceptionUnwind.java b/substratevm/src/com.oracle.svm.core.graal.llvm/src/com/oracle/svm/core/graal/llvm/runtime/LLVMExceptionUnwind.java
index 534db288dddb..b9953d72aa34 100644
--- a/substratevm/src/com.oracle.svm.core.graal.llvm/src/com/oracle/svm/core/graal/llvm/runtime/LLVMExceptionUnwind.java
+++ b/substratevm/src/com.oracle.svm.core.graal.llvm/src/com/oracle/svm/core/graal/llvm/runtime/LLVMExceptionUnwind.java
@@ -115,7 +115,7 @@ public static Throwable retrieveException() {
         return exception;
     }
 
-    private static class IncludeForLLVMOnly implements BooleanSupplier {
+    private static final class IncludeForLLVMOnly implements BooleanSupplier {
         @Override
         public boolean getAsBoolean() {
             return SubstrateOptions.useLLVMBackend();
diff --git a/substratevm/src/com.oracle.svm.core.graal.llvm/src/com/oracle/svm/core/graal/llvm/util/LLVMObjectFileReader.java b/substratevm/src/com.oracle.svm.core.graal.llvm/src/com/oracle/svm/core/graal/llvm/util/LLVMObjectFileReader.java
index 1fed6b3517fd..969d824f3fea 100644
--- a/substratevm/src/com.oracle.svm.core.graal.llvm/src/com/oracle/svm/core/graal/llvm/util/LLVMObjectFileReader.java
+++ b/substratevm/src/com.oracle.svm.core.graal.llvm/src/com/oracle/svm/core/graal/llvm/util/LLVMObjectFileReader.java
@@ -80,7 +80,7 @@ private interface SymbolReader<Symbol> {
         Symbol apply(LLVMSymbolIteratorRef symbolIterator, LLVMSectionIteratorRef sectionIterator);
     }
 
-    private static class LLVMSectionInfo<Section, Symbol> {
+    private static final class LLVMSectionInfo<Section, Symbol> {
         private Section sectionInfo;
         private List<Symbol> symbolInfo = new ArrayList<>();
     }
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/DebugHelper.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/DebugHelper.java
index ec2cbcb86cea..f41c906804ff 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/DebugHelper.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/DebugHelper.java
@@ -331,7 +331,7 @@ private static boolean isReference(DynamicHub hub) {
     }
 
     @Platforms(Platform.HOSTED_ONLY.class)
-    private static class IncludeDebugHelperMethods implements BooleanSupplier {
+    private static final class IncludeDebugHelperMethods implements BooleanSupplier {
         @Override
         public boolean getAsBoolean() {
             return SubstrateOptions.IncludeDebugHelperMethods.getValue();
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/JavaMainWrapper.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/JavaMainWrapper.java
index bb18e8e369af..497a1ce6e621 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/JavaMainWrapper.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/JavaMainWrapper.java
@@ -341,7 +341,7 @@ private static int doRunInNewThread(int argc, CCharPointerPointer argv) {
 
     private static final CGlobalData<CFunctionPointer> RUN_MAIN_ROUTINE = CGlobalDataFactory.forSymbol("__svm_JavaMainWrapper_runMainRoutine");
 
-    private static class RunMainInNewThreadBooleanSupplier implements BooleanSupplier {
+    private static final class RunMainInNewThreadBooleanSupplier implements BooleanSupplier {
         @Override
         public boolean getAsBoolean() {
             if (!ImageSingletons.contains(JavaMainSupport.class)) {
@@ -438,7 +438,7 @@ public static String getCRuntimeArgument0() {
         return CTypeConversion.toJavaString(MAIN_ISOLATE_PARAMETERS.get().getArgv().read(0));
     }
 
-    private static class EnterCreateIsolateWithCArgumentsPrologue implements CEntryPointOptions.Prologue {
+    private static final class EnterCreateIsolateWithCArgumentsPrologue implements CEntryPointOptions.Prologue {
         private static final CGlobalData<CCharPointer> errorMessage = CGlobalDataFactory.createCString(
                         "Failed to create the main Isolate.");
 
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/SubstrateDiagnostics.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/SubstrateDiagnostics.java
index f6c6809c52e0..57b31d6bd348 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/SubstrateDiagnostics.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/SubstrateDiagnostics.java
@@ -568,7 +568,7 @@ public void clear() {
         }
     }
 
-    private static class DumpRegisters extends DiagnosticThunk {
+    private static final class DumpRegisters extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 4;
@@ -590,7 +590,7 @@ public void printDiagnostics(Log log, ErrorContext context, int maxDiagnosticLev
         }
     }
 
-    private static class DumpInstructions extends DiagnosticThunk {
+    private static final class DumpInstructions extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 4;
@@ -638,7 +638,7 @@ private static void hexDump(Log log, CodePointer ip, int bytesBefore, int bytesA
         }
     }
 
-    private static class DumpTopOfCurrentThreadStack extends DiagnosticThunk {
+    private static final class DumpTopOfCurrentThreadStack extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 1;
@@ -699,7 +699,7 @@ public void printDiagnostics(Log log, ErrorContext context, int maxDiagnosticLev
         }
     }
 
-    private static class DumpThreads extends DiagnosticThunk {
+    private static final class DumpThreads extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 3;
@@ -750,7 +750,7 @@ public void printDiagnostics(Log log, ErrorContext context, int maxDiagnosticLev
         }
     }
 
-    private static class DumpCurrentThreadLocals extends DiagnosticThunk {
+    private static final class DumpCurrentThreadLocals extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 2;
@@ -774,7 +774,7 @@ public void printDiagnostics(Log log, ErrorContext context, int maxDiagnosticLev
         }
     }
 
-    private static class DumpCurrentVMOperation extends DiagnosticThunk {
+    private static final class DumpCurrentVMOperation extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 2;
@@ -789,7 +789,7 @@ public void printDiagnostics(Log log, ErrorContext context, int maxDiagnosticLev
         }
     }
 
-    private static class DumpVMOperationHistory extends DiagnosticThunk {
+    private static final class DumpVMOperationHistory extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 2;
@@ -973,7 +973,7 @@ private static UnsignedWord getContainerPhysicalMemory() {
         }
     }
 
-    private static class DumpCounters extends DiagnosticThunk {
+    private static final class DumpCounters extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 1;
@@ -991,7 +991,7 @@ public void printDiagnostics(Log log, ErrorContext context, int maxDiagnosticLev
         }
     }
 
-    private static class DumpCurrentThreadFrameAnchors extends DiagnosticThunk {
+    private static final class DumpCurrentThreadFrameAnchors extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 1;
@@ -1007,7 +1007,7 @@ public void printDiagnostics(Log log, ErrorContext context, int maxDiagnosticLev
         }
     }
 
-    private static class DumpCurrentThreadDecodedStackTrace extends DiagnosticThunk {
+    private static final class DumpCurrentThreadDecodedStackTrace extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 3;
@@ -1055,7 +1055,7 @@ private static void startStackWalkInMostLikelyCaller(Log log, int invocationCoun
         }
     }
 
-    private static class DumpOtherStackTraces extends DiagnosticThunk {
+    private static final class DumpOtherStackTraces extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 3;
@@ -1103,7 +1103,7 @@ private static void printStackTrace(Log log, IsolateThread vmThread, int invocat
         }
     }
 
-    private static class DumpCommandLine extends DiagnosticThunk {
+    private static final class DumpCommandLine extends DiagnosticThunk {
         @Override
         public int maxInvocationCount() {
             return 1;
@@ -1123,7 +1123,7 @@ public void printDiagnostics(Log log, ErrorContext context, int maxDiagnosticLev
         }
     }
 
-    private static class ImageCodeLocationInfoPrinter {
+    private static final class ImageCodeLocationInfoPrinter {
         private final CodeInfoDecoder.FrameInfoCursor frameInfoCursor = new CodeInfoDecoder.FrameInfoCursor();
 
         /**
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/CodeInfoDecoder.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/CodeInfoDecoder.java
index 4a6e99458239..c91a875a5831 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/CodeInfoDecoder.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/CodeInfoDecoder.java
@@ -758,7 +758,7 @@ public FrameInfoState reset() {
         }
     }
 
-    private static class SingleShotFrameInfoQueryResultAllocator implements FrameInfoDecoder.FrameInfoQueryResultAllocator {
+    private static final class SingleShotFrameInfoQueryResultAllocator implements FrameInfoDecoder.FrameInfoQueryResultAllocator {
         private final FrameInfoQueryResult frameInfoQueryResult = new FrameInfoQueryResult();
         private boolean fired;
 
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/FrameInfoDecoder.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/FrameInfoDecoder.java
index 19f26c790bc9..cfe4647edf55 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/FrameInfoDecoder.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/FrameInfoDecoder.java
@@ -208,7 +208,7 @@ public void decodeConstant(ValueInfo valueInfo, NonmovableObjectArray<?> frameIn
 
     static final HeapBasedValueInfoAllocator HeapBasedValueInfoAllocator = new HeapBasedValueInfoAllocator();
 
-    private static class CompressedFrameDecoderHelper {
+    private static final class CompressedFrameDecoderHelper {
         /**
          * Differentiates between compressed and uncompressed frame slices. Uncompressed frame
          * slices start with {@link #UNCOMPRESSED_FRAME_SLICE_MARKER}.
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/FrameInfoEncoder.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/FrameInfoEncoder.java
index 1634beabd0a6..8454d08dc8b7 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/FrameInfoEncoder.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/FrameInfoEncoder.java
@@ -236,7 +236,7 @@ record CompressedFrameData(
      * compressed and uncompressed frame slices, uncompressed frame slices start with the
      * {@link FrameInfoDecoder#UNCOMPRESSED_FRAME_SLICE_MARKER}.
      */
-    private static class CompressedFrameInfoEncodingMetadata {
+    private static final class CompressedFrameInfoEncodingMetadata {
         final List<CompressedFrameData> framesToEncode = new ArrayList<>();
         final EconomicMap<CompressedFrameData, Integer> framesToEncodeIndexMap = EconomicMap.create(Equivalence.DEFAULT);
         final List<List<CompressedFrameData>> frameSlices = new ArrayList<>();
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/container/Container.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/container/Container.java
index 75892227f5e8..c20a0af1e969 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/container/Container.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/container/Container.java
@@ -175,7 +175,7 @@ public long getCachedMemoryLimitInBytes() {
         return cachedMemoryLimitInBytes;
     }
 
-    private static class State {
+    private static final class State {
         static final UnsignedWord UNINITIALIZED = Word.unsigned(0);
         static final UnsignedWord INITIALIZING = Word.unsigned(1);
         static final UnsignedWord NOT_CONTAINERIZED = Word.unsigned(2);
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/graal/snippets/NonSnippetLowerings.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/graal/snippets/NonSnippetLowerings.java
index 60f8ed9ba6ea..a38f4f1a4253 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/graal/snippets/NonSnippetLowerings.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/graal/snippets/NonSnippetLowerings.java
@@ -235,7 +235,7 @@ private ForeignCallDescriptor lookupBytecodeException(BytecodeExceptionKind exce
         return descriptor;
     }
 
-    private class BytecodeExceptionLowering implements NodeLoweringProvider<BytecodeExceptionNode> {
+    private final class BytecodeExceptionLowering implements NodeLoweringProvider<BytecodeExceptionNode> {
         @Override
         public void lower(BytecodeExceptionNode node, LoweringTool tool) {
             if (tool.getLoweringStage() == StandardLoweringStage.HIGH_TIER) {
@@ -256,7 +256,7 @@ public void lower(BytecodeExceptionNode node, LoweringTool tool) {
         }
     }
 
-    private class ThrowBytecodeExceptionLowering implements NodeLoweringProvider<ThrowBytecodeExceptionNode> {
+    private final class ThrowBytecodeExceptionLowering implements NodeLoweringProvider<ThrowBytecodeExceptionNode> {
         @Override
         public void lower(ThrowBytecodeExceptionNode node, LoweringTool tool) {
             if (tool.getLoweringStage() == StandardLoweringStage.HIGH_TIER) {
@@ -279,7 +279,7 @@ public void lower(ThrowBytecodeExceptionNode node, LoweringTool tool) {
         }
     }
 
-    private static class GetClassLowering implements NodeLoweringProvider<GetClassNode> {
+    private static final class GetClassLowering implements NodeLoweringProvider<GetClassNode> {
         @Override
         public void lower(GetClassNode node, LoweringTool tool) {
             StampProvider stampProvider = tool.getStampProvider();
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/graal/snippets/SubstrateAllocationSnippets.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/graal/snippets/SubstrateAllocationSnippets.java
index bcdab1271587..657a47069e9f 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/graal/snippets/SubstrateAllocationSnippets.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/graal/snippets/SubstrateAllocationSnippets.java
@@ -762,7 +762,7 @@ private static boolean shouldForceSlowPath(StructuredGraph graph) {
             return GraalOptions.ReduceCodeSize.getValue(graph.getOptions());
         }
 
-        private class NewInstanceLowering implements NodeLoweringProvider<NewInstanceNode> {
+        private final class NewInstanceLowering implements NodeLoweringProvider<NewInstanceNode> {
             @Override
             public void lower(NewInstanceNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -789,7 +789,7 @@ public void lower(NewInstanceNode node, LoweringTool tool) {
             }
         }
 
-        private class NewInstanceWithExceptionLowering implements NodeLoweringProvider<NewInstanceWithExceptionNode> {
+        private final class NewInstanceWithExceptionLowering implements NodeLoweringProvider<NewInstanceWithExceptionNode> {
             @Override
             public void lower(NewInstanceWithExceptionNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -815,7 +815,7 @@ public void lower(NewInstanceWithExceptionNode node, LoweringTool tool) {
             }
         }
 
-        private class NewHybridInstanceLowering implements NodeLoweringProvider<SubstrateNewHybridInstanceNode> {
+        private final class NewHybridInstanceLowering implements NodeLoweringProvider<SubstrateNewHybridInstanceNode> {
             @Override
             public void lower(SubstrateNewHybridInstanceNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -852,7 +852,7 @@ public void lower(SubstrateNewHybridInstanceNode node, LoweringTool tool) {
             }
         }
 
-        private class NewStoredContinuationLowering implements NodeLoweringProvider<NewStoredContinuationNode> {
+        private final class NewStoredContinuationLowering implements NodeLoweringProvider<NewStoredContinuationNode> {
             @Override
             public void lower(NewStoredContinuationNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -883,7 +883,7 @@ public void lower(NewStoredContinuationNode node, LoweringTool tool) {
             }
         }
 
-        private class NewArrayLowering implements NodeLoweringProvider<NewArrayNode> {
+        private final class NewArrayLowering implements NodeLoweringProvider<NewArrayNode> {
             @Override
             public void lower(NewArrayNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -917,7 +917,7 @@ public void lower(NewArrayNode node, LoweringTool tool) {
             }
         }
 
-        private class NewArrayWithExceptionLowering implements NodeLoweringProvider<NewArrayWithExceptionNode> {
+        private final class NewArrayWithExceptionLowering implements NodeLoweringProvider<NewArrayWithExceptionNode> {
             @Override
             public void lower(NewArrayWithExceptionNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -952,7 +952,7 @@ public void lower(NewArrayWithExceptionNode node, LoweringTool tool) {
             }
         }
 
-        private class NewMultiArrayLowering implements NodeLoweringProvider<NewMultiArrayNode> {
+        private final class NewMultiArrayLowering implements NodeLoweringProvider<NewMultiArrayNode> {
             @Override
             public void lower(NewMultiArrayNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -979,7 +979,7 @@ public void lower(NewMultiArrayNode node, LoweringTool tool) {
             }
         }
 
-        private class NewMultiArrayWithExceptionLowering implements NodeLoweringProvider<NewMultiArrayWithExceptionNode> {
+        private final class NewMultiArrayWithExceptionLowering implements NodeLoweringProvider<NewMultiArrayWithExceptionNode> {
             @Override
             public void lower(NewMultiArrayWithExceptionNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -1006,7 +1006,7 @@ public void lower(NewMultiArrayWithExceptionNode node, LoweringTool tool) {
             }
         }
 
-        private class DynamicNewInstanceLowering implements NodeLoweringProvider<DynamicNewInstanceNode> {
+        private final class DynamicNewInstanceLowering implements NodeLoweringProvider<DynamicNewInstanceNode> {
             @Override
             public void lower(DynamicNewInstanceNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -1028,7 +1028,7 @@ public void lower(DynamicNewInstanceNode node, LoweringTool tool) {
             }
         }
 
-        private class DynamicNewInstanceWithExceptionLowering implements NodeLoweringProvider<DynamicNewInstanceWithExceptionNode> {
+        private final class DynamicNewInstanceWithExceptionLowering implements NodeLoweringProvider<DynamicNewInstanceWithExceptionNode> {
             @Override
             public void lower(DynamicNewInstanceWithExceptionNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -1050,7 +1050,7 @@ public void lower(DynamicNewInstanceWithExceptionNode node, LoweringTool tool) {
             }
         }
 
-        private class DynamicNewArrayLowering implements NodeLoweringProvider<DynamicNewArrayNode> {
+        private final class DynamicNewArrayLowering implements NodeLoweringProvider<DynamicNewArrayNode> {
             @Override
             public void lower(DynamicNewArrayNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -1073,7 +1073,7 @@ public void lower(DynamicNewArrayNode node, LoweringTool tool) {
             }
         }
 
-        private class DynamicNewArrayWithExceptionLowering implements NodeLoweringProvider<DynamicNewArrayWithExceptionNode> {
+        private final class DynamicNewArrayWithExceptionLowering implements NodeLoweringProvider<DynamicNewArrayWithExceptionNode> {
             @Override
             public void lower(DynamicNewArrayWithExceptionNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -1096,7 +1096,7 @@ public void lower(DynamicNewArrayWithExceptionNode node, LoweringTool tool) {
             }
         }
 
-        private class ValidateNewInstanceClassLowering implements NodeLoweringProvider<ValidateNewInstanceClassNode> {
+        private final class ValidateNewInstanceClassLowering implements NodeLoweringProvider<ValidateNewInstanceClassNode> {
             @Override
             public void lower(ValidateNewInstanceClassNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -1108,7 +1108,7 @@ public void lower(ValidateNewInstanceClassNode node, LoweringTool tool) {
             }
         }
 
-        private class NewPodInstanceLowering implements NodeLoweringProvider<NewPodInstanceNode> {
+        private final class NewPodInstanceLowering implements NodeLoweringProvider<NewPodInstanceNode> {
             @Override
             public void lower(NewPodInstanceNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
@@ -1135,7 +1135,7 @@ public void lower(NewPodInstanceNode node, LoweringTool tool) {
             }
         }
 
-        private class NewDynamicHubLowering implements NodeLoweringProvider<SubstrateNewDynamicHubNode> {
+        private final class NewDynamicHubLowering implements NodeLoweringProvider<SubstrateNewDynamicHubNode> {
             @Override
             public void lower(SubstrateNewDynamicHubNode node, LoweringTool tool) {
                 StructuredGraph graph = node.graph();
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/dump/HeapDumpMetadata.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/dump/HeapDumpMetadata.java
index 79f73b148ae6..465402c7f2ef 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/dump/HeapDumpMetadata.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/dump/HeapDumpMetadata.java
@@ -426,7 +426,7 @@ public interface FieldNamePointer extends PointerBase {
         FieldName read();
     }
 
-    private static class ComputeHubDataVisitor implements ObjectVisitor {
+    private static final class ComputeHubDataVisitor implements ObjectVisitor {
         private int classSerialNum;
 
         public void initialize() {
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/dump/HeapDumpWriter.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/dump/HeapDumpWriter.java
index 196999b34800..e2fa4ec17412 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/dump/HeapDumpWriter.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/dump/HeapDumpWriter.java
@@ -1438,6 +1438,6 @@ private void markThreadLocalAsGCRoot(Object obj) {
         }
     }
 
-    private static class UnknownClass {
+    private static final class UnknownClass {
     }
 }
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/hub/DynamicHub.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/hub/DynamicHub.java
index f329bf51111d..7a942170df11 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/hub/DynamicHub.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/hub/DynamicHub.java
@@ -2137,35 +2137,35 @@ public boolean isReached() {
         return classInitializationInfo.isTypeReached(this);
     }
 
-    private static class ReflectionDataAccessors {
+    private static final class ReflectionDataAccessors {
         @SuppressWarnings("unused")
         private static SoftReference<Target_java_lang_Class_ReflectionData<?>> getReflectionData(DynamicHub that) {
             return that.companion.getReflectionData();
         }
     }
 
-    private static class ClassLoaderAccessors {
+    private static final class ClassLoaderAccessors {
         @SuppressWarnings("unused")
         private static ClassLoader getClassLoader(DynamicHub that) {
             return that.companion.getClassLoader();
         }
     }
 
-    private static class AnnotationDataAccessors {
+    private static final class AnnotationDataAccessors {
         @SuppressWarnings("unused")
         private static Target_java_lang_Class_AnnotationData getAnnotationData(DynamicHub that) {
             return that.companion.getAnnotationData();
         }
     }
 
-    private static class AnnotationTypeAccessors {
+    private static final class AnnotationTypeAccessors {
         @SuppressWarnings("unused")
         private static AnnotationType getAnnotationType(DynamicHub that) {
             return that.companion.getAnnotationType();
         }
     }
 
-    private static class CachedConstructorAccessors {
+    private static final class CachedConstructorAccessors {
         @SuppressWarnings("unused")
         private static Constructor<?> getCachedConstructor(DynamicHub that) {
             /*
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/localization/substitutions/Target_java_util_Locale.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/localization/substitutions/Target_java_util_Locale.java
index 9b4473c24702..1ad0e9f5acdb 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/localization/substitutions/Target_java_util_Locale.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jdk/localization/substitutions/Target_java_util_Locale.java
@@ -45,7 +45,7 @@ final class Target_java_util_Locale {
     private static native Locale initDefault();
 
     @SuppressWarnings("unused")
-    private static class DefaultLocaleAccessors {
+    private static final class DefaultLocaleAccessors {
         static Locale get() {
             if (Util_java_util_Locale.injectedDefaultLocale == null) {
                 Util_java_util_Locale.injectedDefaultLocale = Target_java_util_Locale.initDefault();
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/JfrSymbolRepository.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/JfrSymbolRepository.java
index 57f8e1a9452b..9502dbd4d652 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/JfrSymbolRepository.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/JfrSymbolRepository.java
@@ -245,7 +245,7 @@ void teardown() {
         }
     }
 
-    private static class ReplaceDotWithSlash implements CharReplacer {
+    private static final class ReplaceDotWithSlash implements CharReplacer {
         @Override
         @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
         public char replace(char ch) {
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/JfrTypeRepository.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/JfrTypeRepository.java
index 92cb6ee979e6..bd8d8f7f2d9f 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/JfrTypeRepository.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jfr/JfrTypeRepository.java
@@ -327,7 +327,7 @@ private void clearEpochData() {
         currentClassLoaderId = 0;
     }
 
-    private static class TypeInfo {
+    private static final class TypeInfo {
         final Set<Class<?>> classes = new HashSet<>();
         final Map<String, PackageInfo> packages = new HashMap<>();
         final Map<Module, Long> modules = new HashMap<>();
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jvmti/JvmtiFunctions.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jvmti/JvmtiFunctions.java
index 6e0fd4c70286..78d7fdff7e3e 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jvmti/JvmtiFunctions.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/jvmti/JvmtiFunctions.java
@@ -1386,7 +1386,7 @@ static int SetHeapSamplingInterval(JvmtiExternalEnv externalEnv, int samplingInt
 
     // Checkstyle: resume
 
-    private static class JvmtiEnvEnterPrologue implements CEntryPointOptions.Prologue {
+    private static final class JvmtiEnvEnterPrologue implements CEntryPointOptions.Prologue {
         /**
          * In the prologue, we need to be careful that we don't access any image heap data before
          * the heap base is set up, so we use @CConstant instead of @CEnum.
diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/log/RealLog.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/log/RealLog.java
index 819e36de937f..e8b61e8650d9 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/log/RealLog.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/log/RealLog.java
@@ -733,9 +733,9 @@ private void printRemainingFramesCount(int remaining) {
         }
     }
 
-    private class BacktracePrinter extends BacktraceDecoder {
+    private final class BacktracePrinter extends BacktraceDecoder {
 
-        protected final int printBacktrace(long[] backtrace, int maxFramesProcessed) {
+        protected int printBacktrace(long[] backtrace, int maxFramesProcessed) {
             return visitBacktrace(backtrace, maxFramesProcessed, SubstrateOptions.maxJavaStackTraceDepth());
         }
 
diff --git a/substratevm/src/com.oracle.svm.driver/src/com/oracle/svm/driver/ArgFilesOptionPreprocessor.java b/substratevm/src/com.oracle.svm.driver/src/com/oracle/svm/driver/ArgFilesOptionPreprocessor.java
index 99a28e723261..1dfd37903942 100644
--- a/substratevm/src/com.oracle.svm.driver/src/com/oracle/svm/driver/ArgFilesOptionPreprocessor.java
+++ b/substratevm/src/com.oracle.svm.driver/src/com/oracle/svm/driver/ArgFilesOptionPreprocessor.java
@@ -71,7 +71,7 @@ private enum PARSER_STATE {
         IN_TOKEN
     }
 
-    private static class CTX_ARGS {
+    private static final class CTX_ARGS {
         PARSER_STATE state;
         int cptr;
         int eob;
diff --git a/substratevm/src/com.oracle.svm.graal.hotspot.libgraal/src/com/oracle/svm/graal/hotspot/libgraal/LibGraalSubstitutions.java b/substratevm/src/com.oracle.svm.graal.hotspot.libgraal/src/com/oracle/svm/graal/hotspot/libgraal/LibGraalSubstitutions.java
index 3a70db24f24b..14b29ffd7afd 100644
--- a/substratevm/src/com.oracle.svm.graal.hotspot.libgraal/src/com/oracle/svm/graal/hotspot/libgraal/LibGraalSubstitutions.java
+++ b/substratevm/src/com.oracle.svm.graal.hotspot.libgraal/src/com/oracle/svm/graal/hotspot/libgraal/LibGraalSubstitutions.java
@@ -203,7 +203,7 @@ private long getAddress() {
      * instance at image build-time. This FieldValueTransformer ensures that.
      */
     @Platforms(HOSTED_ONLY.class)
-    private static class GlobalAtomicLongAddressProvider implements FieldValueTransformer {
+    private static final class GlobalAtomicLongAddressProvider implements FieldValueTransformer {
         @Override
         public Object transform(Object receiver, Object originalValue) {
             long initialValue;
diff --git a/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/hosted/runtimecompilation/RuntimeCompilationFeature.java b/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/hosted/runtimecompilation/RuntimeCompilationFeature.java
index 62d5d91f9c9d..ba21dd662f55 100644
--- a/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/hosted/runtimecompilation/RuntimeCompilationFeature.java
+++ b/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/hosted/runtimecompilation/RuntimeCompilationFeature.java
@@ -622,7 +622,7 @@ private void printFailingRuntimeMethodTrace(CallTreeInfo treeInfo, AnalysisMetho
         }
     }
 
-    private class RuntimeCompilationParsingSupport implements SVMParsingSupport {
+    private final class RuntimeCompilationParsingSupport implements SVMParsingSupport {
         RuntimeCompilationInlineBeforeAnalysisPolicy runtimeInlineBeforeAnalysisPolicy = null;
 
         @Override
@@ -966,7 +966,7 @@ private static <T extends AnalysisMethod> T getFullRuntimeVersion(BigBang bb, T
         return (T) runtimeMethod;
     }
 
-    private class RuntimeCompilationAnalysisPolicy implements HostVM.MultiMethodAnalysisPolicy {
+    private final class RuntimeCompilationAnalysisPolicy implements HostVM.MultiMethodAnalysisPolicy {
 
         @Override
         public <T extends AnalysisMethod> Collection<T> determineCallees(BigBang bb, T implementation, T target, MultiMethod.MultiMethodKey callerMultiMethodKey, InvokeTypeFlow invokeFlow) {
diff --git a/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/hosted/runtimecompilation/RuntimeCompiledMethodSupport.java b/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/hosted/runtimecompilation/RuntimeCompiledMethodSupport.java
index acb6133742e9..f7d6983baf61 100644
--- a/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/hosted/runtimecompilation/RuntimeCompiledMethodSupport.java
+++ b/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/hosted/runtimecompilation/RuntimeCompiledMethodSupport.java
@@ -499,7 +499,7 @@ protected void run(StructuredGraph graph) {
      * Removes {@link DeoptEntryNode}s, {@link DeoptProxyAnchorNode}s, and {@link DeoptProxyNode}s
      * which are determined to be unnecessary after the runtime compilation methods are optimized.
      */
-    private static class RemoveUnneededDeoptSupport extends Phase {
+    private static final class RemoveUnneededDeoptSupport extends Phase {
         enum RemovalDecision {
             KEEP,
             PROXIFY,
@@ -545,7 +545,7 @@ protected void run(StructuredGraph graph) {
             }
         }
 
-        RemovalDecision getDecision(StateSplit node, EconomicMap<StateSplit, RemovalDecision> decisionCache) {
+        static RemovalDecision getDecision(StateSplit node, EconomicMap<StateSplit, RemovalDecision> decisionCache) {
             RemovalDecision cached = decisionCache.get(node);
             if (cached != null) {
                 return cached;
diff --git a/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/meta/RuntimeCodeInstaller.java b/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/meta/RuntimeCodeInstaller.java
index acf3c18576ff..5682a635e08e 100644
--- a/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/meta/RuntimeCodeInstaller.java
+++ b/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/meta/RuntimeCodeInstaller.java
@@ -300,7 +300,7 @@ private int patchData(Map<Integer, NativeImagePatcher> patcher, ObjectConstantsH
         return patchesHandled;
     }
 
-    private static class RuntimeFrameInfoCustomization extends FrameInfoEncoder.SourceFieldsFromImage {
+    private static final class RuntimeFrameInfoCustomization extends FrameInfoEncoder.SourceFieldsFromImage {
         @Override
         protected boolean storeDeoptTargetMethod() {
             return true;
diff --git a/substratevm/src/com.oracle.svm.hosted.foreign/src/com/oracle/svm/hosted/foreign/ForeignFunctionsFeature.java b/substratevm/src/com.oracle.svm.hosted.foreign/src/com/oracle/svm/hosted/foreign/ForeignFunctionsFeature.java
index f673d4329c47..4fe28ec02cde 100644
--- a/substratevm/src/com.oracle.svm.hosted.foreign/src/com/oracle/svm/hosted/foreign/ForeignFunctionsFeature.java
+++ b/substratevm/src/com.oracle.svm.hosted.foreign/src/com/oracle/svm/hosted/foreign/ForeignFunctionsFeature.java
@@ -164,7 +164,7 @@ public int hashCode() {
         }
     }
 
-    private class RuntimeForeignAccessSupportImpl extends ConditionalConfigurationRegistry implements StronglyTypedRuntimeForeignAccessSupport {
+    private final class RuntimeForeignAccessSupportImpl extends ConditionalConfigurationRegistry implements StronglyTypedRuntimeForeignAccessSupport {
 
         private final Lookup implLookup = ReflectionUtil.readStaticField(MethodHandles.Lookup.class, "IMPL_LOOKUP");
 
@@ -186,7 +186,7 @@ public void registerForDirectUpcall(ConfigurationCondition condition, MethodHand
             DirectMethodHandleDesc directMethodHandleDesc = target.describeConstable()
                             .filter(x -> x instanceof DirectMethodHandleDesc dmh && dmh.kind() == Kind.STATIC)
                             .map(x -> ((DirectMethodHandleDesc) x))
-                            .orElseThrow(() -> new IllegalArgumentException("target must be a direct method handle to a static method"));
+                            .orElseThrow(() -> new IllegalArgumentException("Target must be a direct method handle to a static method"));
             /*
              * The call 'implLookup.revealDirect' can only succeed if the method handle is
              * crackable. The call is expected to succeed because we already call
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/ClassPredefinitionFeature.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/ClassPredefinitionFeature.java
index 0aa2d92bb2e1..b5eedb2c7aa0 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/ClassPredefinitionFeature.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/ClassPredefinitionFeature.java
@@ -152,7 +152,7 @@ public void beforeAnalysis(BeforeAnalysisAccess access) {
         }
     }
 
-    private class PredefinedClassesRegistryImpl implements PredefinedClassesRegistry {
+    private final class PredefinedClassesRegistryImpl implements PredefinedClassesRegistry {
         @Override
         public void add(String nameInfo, String providedHash, URI baseUri) {
             if (!PredefinedClassesSupport.supportsBytecodes()) {
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageClassLoader.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageClassLoader.java
index d92e5cea00ca..59e3ecfc338d 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageClassLoader.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageClassLoader.java
@@ -794,7 +794,7 @@ private static ModuleReader createModuleReader(ModuleReference mref) {
     /**
      * See {@code jdk.internal.loader.Loader#NullModuleReader}.
      */
-    private static class NullModuleReader implements ModuleReader {
+    private static final class NullModuleReader implements ModuleReader {
         @Override
         public Optional<URI> find(String name) {
             return Optional.empty();
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageSystemIOWrappers.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageSystemIOWrappers.java
index 77e2a7f80744..ce9830fa7539 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageSystemIOWrappers.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/NativeImageSystemIOWrappers.java
@@ -109,7 +109,7 @@ private void maybeInformProgressReporterOnce() {
         }
     }
 
-    private static class NativeImageSystemIOWrappersDisabled extends NativeImageSystemIOWrappers {
+    private static final class NativeImageSystemIOWrappersDisabled extends NativeImageSystemIOWrappers {
         private static final PrintStream NULL_PRINT_STREAM = new PrintStream(OutputStream.nullOutputStream());
 
         @Override
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/OpenTypeWorldFeature.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/OpenTypeWorldFeature.java
index d15f230c9fad..7bea88352544 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/OpenTypeWorldFeature.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/OpenTypeWorldFeature.java
@@ -164,7 +164,7 @@ public int hashCode() {
         }
     }
 
-    private static class LayerTypeCheckInfo implements LayeredImageSingleton {
+    private static final class LayerTypeCheckInfo implements LayeredImageSingleton {
         Map<Integer, TypeCheckInfo> identifierToTypeInfo = new HashMap<>();
         int maxTypeID = 0;
 
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/ProgressReporter.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/ProgressReporter.java
index a313f80ec77e..cf8debbbbd27 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/ProgressReporter.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/ProgressReporter.java
@@ -886,7 +886,7 @@ private static OperatingSystemMXBean getOperatingSystemMXBean() {
         return (OperatingSystemMXBean) ManagementFactory.getOperatingSystemMXBean();
     }
 
-    private static class Utils {
+    private static final class Utils {
         private static final double MILLIS_TO_SECONDS = 1000d;
         private static final double NANOS_TO_SECONDS = 1000d * 1000d * 1000d;
 
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/SubstitutionReportFeature.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/SubstitutionReportFeature.java
index 5bb641c25f80..98ef8061311a 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/SubstitutionReportFeature.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/SubstitutionReportFeature.java
@@ -155,7 +155,7 @@ private static <T> String formatSubstitution(String jar, String type, T original
         return '\'' + jar + "'," + type + ',' + formatter.apply(original) + ',' + formatter.apply(annotated);
     }
 
-    private static class Substitutions {
+    private static final class Substitutions {
         private final Map<ResolvedJavaType, ResolvedJavaType> substitutedTypes = new TreeMap<>(Comparator.comparing(SubstitutionReportFeature::formatType));
         private final Map<ResolvedJavaMethod, ResolvedJavaMethod> substitutedMethods = new TreeMap<>(Comparator.comparing(SubstitutionReportFeature::formatMethod));
         private final Map<ResolvedJavaField, ResolvedJavaField> substitutedFields = new TreeMap<>(Comparator.comparing(SubstitutionReportFeature::formatField));
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/code/CEntryPointCallStubMethod.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/code/CEntryPointCallStubMethod.java
index 9cdfa4b61c40..0cd79b174e31 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/code/CEntryPointCallStubMethod.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/code/CEntryPointCallStubMethod.java
@@ -446,7 +446,7 @@ private static InvokeWithExceptionNode generatePrologueOrEpilogueInvoke(Substrat
         return invoke;
     }
 
-    private static class ExecutionContextParameters {
+    private static final class ExecutionContextParameters {
         int isolateCount = 0;
         int lastIsolateIndex = -1;
         int designatedIsolateIndex = -1;
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/dashboard/HeapBreakdown.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/dashboard/HeapBreakdown.java
index a71fc49af37d..2cc509b68068 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/dashboard/HeapBreakdown.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/dashboard/HeapBreakdown.java
@@ -51,7 +51,7 @@ Map<String, Long[]> getData() {
         return sizes.entrySet().stream().collect(Collectors.toMap(Entry::getKey, (Entry<String, Statistics> e) -> new Long[]{e.getValue().size, e.getValue().count}));
     }
 
-    private static class Statistics {
+    private static final class Statistics {
         long size = 0;
         long count = 0;
     }
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/dashboard/PointsToBreakdown.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/dashboard/PointsToBreakdown.java
index 66770332b009..b5620ec77d06 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/dashboard/PointsToBreakdown.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/dashboard/PointsToBreakdown.java
@@ -233,7 +233,7 @@ static class Port {
         }
     }
 
-    private static class PointToStructure implements GraphStructure<PointsToBreakdown, AnalysisWrapper, WrapperClazz, Port> {
+    private static final class PointToStructure implements GraphStructure<PointsToBreakdown, AnalysisWrapper, WrapperClazz, Port> {
         enum EMPT {
             EDGE
         }
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/NativeImageCodeCache.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/NativeImageCodeCache.java
index 4a45b8784331..f348152cc099 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/NativeImageCodeCache.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/NativeImageCodeCache.java
@@ -735,7 +735,7 @@ private void printCompilationResults(PrintWriter writer) {
 
     }
 
-    private static class HostedFrameInfoCustomization extends FrameInfoEncoder.SourceFieldsFromMethod {
+    private static final class HostedFrameInfoCustomization extends FrameInfoEncoder.SourceFieldsFromMethod {
         int numDeoptEntryPoints;
         int numDuringCallEntryPoints;
 
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/sources/SourceCache.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/sources/SourceCache.java
index 70f8a46965b8..e18f037fe135 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/sources/SourceCache.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/image/sources/SourceCache.java
@@ -63,7 +63,7 @@
 
 public class SourceCache {
 
-    private static class SourceRoots {
+    private static final class SourceRoots {
         /**
          * A list of root directories which may contain source files from which this cache can be
          * populated.
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/jni/JNIAccessFeature.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/jni/JNIAccessFeature.java
index ecd895a00128..d56e64298552 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/jni/JNIAccessFeature.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/jni/JNIAccessFeature.java
@@ -216,7 +216,7 @@ public void afterRegistration(AfterRegistrationAccess arg) {
                         ConfigurationFiles.Options.JNIConfigurationFiles, ConfigurationFiles.Options.JNIConfigurationResources, ConfigurationFile.JNI.getFileName());
     }
 
-    private class JNIRuntimeAccessibilitySupportImpl extends ConditionalConfigurationRegistry
+    private final class JNIRuntimeAccessibilitySupportImpl extends ConditionalConfigurationRegistry
                     implements RuntimeJNIAccessSupport {
 
         @Override
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/meta/TypeCheckBuilder.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/meta/TypeCheckBuilder.java
index 663e6d735db4..d9531e8547be 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/meta/TypeCheckBuilder.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/meta/TypeCheckBuilder.java
@@ -1869,7 +1869,7 @@ static boolean runtimeIsAssignableFrom(HostedType superType, HostedType checkedT
         }
     }
 
-    private static class OpenTypeWorldTypeInfo {
+    private static final class OpenTypeWorldTypeInfo {
 
         /**
          * Within {@link com.oracle.svm.core.hub.DynamicHub} typecheck metadata the ids of the
diff --git a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/reflect/ReflectionGraphKit.java b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/reflect/ReflectionGraphKit.java
index a078629c321f..881d41fc412c 100644
--- a/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/reflect/ReflectionGraphKit.java
+++ b/substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/reflect/ReflectionGraphKit.java
@@ -291,7 +291,7 @@ private ValueNode widenPrimitive(ValueNode unboxedValue, JavaKind fromKind, Java
         if (fromStackKind == toStackKind) {
             return unboxedValue;
         }
-
+        // Checkstyle: stop
         switch (fromStackKind) {
             case Int:
                 switch (toStackKind) {
@@ -323,5 +323,6 @@ private ValueNode widenPrimitive(ValueNode unboxedValue, JavaKind fromKind, Java
             default:
                 throw VMError.shouldNotReachHereUnexpectedInput(fromStackKind); // ExcludeFromJacocoGeneratedReport
         }
+        // Checkstyle: resume
     }
 }
diff --git a/substratevm/src/com.oracle.svm.jdwp.bridge/src/com/oracle/svm/jdwp/bridge/ArgFilesOption.java b/substratevm/src/com.oracle.svm.jdwp.bridge/src/com/oracle/svm/jdwp/bridge/ArgFilesOption.java
index 22f7062fc760..93394cd4ce3c 100644
--- a/substratevm/src/com.oracle.svm.jdwp.bridge/src/com/oracle/svm/jdwp/bridge/ArgFilesOption.java
+++ b/substratevm/src/com.oracle.svm.jdwp.bridge/src/com/oracle/svm/jdwp/bridge/ArgFilesOption.java
@@ -74,7 +74,7 @@ private enum PARSER_STATE {
         IN_TOKEN
     }
 
-    private static class CTX_ARGS {
+    private static final class CTX_ARGS {
         PARSER_STATE state;
         int cptr;
         int eob;
diff --git a/substratevm/src/com.oracle.svm.jdwp.resident/src/com/oracle/svm/jdwp/resident/DebuggingOnDemandHandler.java b/substratevm/src/com.oracle.svm.jdwp.resident/src/com/oracle/svm/jdwp/resident/DebuggingOnDemandHandler.java
index b15b8f28f312..ad5619a34ac1 100644
--- a/substratevm/src/com.oracle.svm.jdwp.resident/src/com/oracle/svm/jdwp/resident/DebuggingOnDemandHandler.java
+++ b/substratevm/src/com.oracle.svm.jdwp.resident/src/com/oracle/svm/jdwp/resident/DebuggingOnDemandHandler.java
@@ -538,7 +538,7 @@ public static boolean suspendDoneOnShellSide() {
      * com.oracle.svm.hosted.ImageClassLoader#findSystemElements for some reason.
      */
     @SuppressWarnings("unused")
-    private static class EntryPointHolder {
+    private static final class EntryPointHolder {
         @Uninterruptible(reason = "Dummy symbol to make HotSpot's native method linking to look for symbols in the main executable. Required to run the JDWP server (debugger) on HotSpot")
         @CEntryPoint(name = "JNI_OnLoad_DEFAULT_NAMESPACE", include = ResidentJDWPFeatureEnabled.class)
         @CEntryPointOptions(prologue = CEntryPointOptions.NoPrologue.class, epilogue = CEntryPointOptions.NoEpilogue.class)
diff --git a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/LambdaClassDeserializationTest.java b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/LambdaClassDeserializationTest.java
index 534de73d68a9..c0fde7884651 100644
--- a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/LambdaClassDeserializationTest.java
+++ b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/LambdaClassDeserializationTest.java
@@ -39,7 +39,7 @@
 // deserializes lambda class
 public class LambdaClassDeserializationTest {
 
-    private static class SerializeLambda {
+    private static final class SerializeLambda {
         public static Function<Integer, String> createLambda() {
             @SuppressWarnings("unchecked")
             Function<Integer, String> lambda = (Function<Integer, String> & Serializable) (x) -> "Value of parameter is " + x;
@@ -53,7 +53,7 @@ public static void serialize(ByteArrayOutputStream byteArrayOutputStream, Serial
         }
     }
 
-    private static class DeserializeLambda {
+    private static final class DeserializeLambda {
         public static Object deserialize(ByteArrayOutputStream byteArrayOutputStream) throws IOException, ClassNotFoundException {
             ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(byteArrayOutputStream.toByteArray());
             ObjectInputStream objectInputStream = new ObjectInputStream(byteArrayInputStream);
diff --git a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/NoHostedAnnotationsTest.java b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/NoHostedAnnotationsTest.java
index 4353cdb7cd22..f1b130fd436e 100644
--- a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/NoHostedAnnotationsTest.java
+++ b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/NoHostedAnnotationsTest.java
@@ -35,7 +35,7 @@
 public class NoHostedAnnotationsTest {
 
     @DuplicatedInNativeCode
-    private static class TestClass {
+    private static final class TestClass {
     }
 
     @Test
diff --git a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/AbstractJfrTest.java b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/AbstractJfrTest.java
index 3d1ba5c5da32..09896542e793 100644
--- a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/AbstractJfrTest.java
+++ b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/AbstractJfrTest.java
@@ -157,7 +157,7 @@ private static boolean isDebuggingEnabled() {
         return debugRecording != null && !"false".equals(debugRecording);
     }
 
-    private static class ChronologicalComparator implements Comparator<RecordedEvent> {
+    private static final class ChronologicalComparator implements Comparator<RecordedEvent> {
         @Override
         public int compare(RecordedEvent e1, RecordedEvent e2) {
             return e1.getEndTime().compareTo(e2.getEndTime());
diff --git a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorEnterEvent.java b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorEnterEvent.java
index 0d38f527c060..ef6aba8397dc 100644
--- a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorEnterEvent.java
+++ b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorEnterEvent.java
@@ -94,7 +94,7 @@ private void validateEvents(List<RecordedEvent> events) {
         assertTrue("Expected monitor blocked event not found", found);
     }
 
-    private class Helper {
+    private final class Helper {
         private synchronized void doWork() throws InterruptedException {
             if (Thread.currentThread().equals(secondThread)) {
                 return; // second thread doesn't need to do work.
diff --git a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorInflateEvent.java b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorInflateEvent.java
index 39e761e7595e..30a80adc5072 100644
--- a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorInflateEvent.java
+++ b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorInflateEvent.java
@@ -94,7 +94,7 @@ private void validateEvents(List<RecordedEvent> events) {
         assertTrue("Expected monitor inflate event not found.", foundCauseEnter);
     }
 
-    private class EnterHelper {
+    private final class EnterHelper {
         volatile boolean passedCheckpoint = false;
 
         synchronized void doWork() throws InterruptedException {
diff --git a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitEvent.java b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitEvent.java
index d31f508bb3d6..3e8ec8df90ef 100644
--- a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitEvent.java
+++ b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitEvent.java
@@ -118,7 +118,7 @@ private void validateEvents(List<RecordedEvent> events) {
                         abs(prodCount - consCount) > 1 || abs(consCount - COUNT) > 1);
     }
 
-    private static class Helper {
+    private static final class Helper {
         private int count = 0;
         private final int bufferSize = 1;
 
diff --git a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitInterruptEvent.java b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitInterruptEvent.java
index 9383d5ada0ef..56f054c0e9a8 100644
--- a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitInterruptEvent.java
+++ b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitInterruptEvent.java
@@ -144,7 +144,7 @@ private void validateEvents(List<RecordedEvent> events) {
                         simpleWaitFound && interruptedFound);
     }
 
-    private class Helper {
+    private final class Helper {
         public synchronized void interrupt() throws InterruptedException {
             if (Thread.currentThread().equals(interruptedThread)) {
                 // Ensure T1 enters critical section first
diff --git a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitNotifyAllEvent.java b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitNotifyAllEvent.java
index 61e8cbf3ca07..6731315a287b 100644
--- a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitNotifyAllEvent.java
+++ b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitNotifyAllEvent.java
@@ -113,7 +113,7 @@ private void validateEvents(List<RecordedEvent> events) {
                         notifierFound && waitersFound == 2);
     }
 
-    private class Helper {
+    private final class Helper {
         public synchronized void doWork() throws InterruptedException {
             if (Thread.currentThread().equals(consumerThread)) {
                 wait(MILLIS);
diff --git a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitTimeoutEvent.java b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitTimeoutEvent.java
index 08b57ac7b3fa..c1df85eb621c 100644
--- a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitTimeoutEvent.java
+++ b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestJavaMonitorWaitTimeoutEvent.java
@@ -139,7 +139,7 @@ private void validateEvents(List<RecordedEvent> events) {
                         simpleWaitFound && timeoutFound);
     }
 
-    private class Helper {
+    private final class Helper {
         public synchronized void timeout() throws InterruptedException {
             wait(MILLIS);
         }
diff --git a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestObjectAllocationInNewTLABEvent.java b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestObjectAllocationInNewTLABEvent.java
index 8e5e9157429a..a002310c53b5 100644
--- a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestObjectAllocationInNewTLABEvent.java
+++ b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestObjectAllocationInNewTLABEvent.java
@@ -127,6 +127,6 @@ private static Helper allocateInstance() {
      * This class is only needed to provide a unique name in the event's "objectClass" field that we
      * check.
      */
-    private static class Helper {
+    private static final class Helper {
     }
 }
diff --git a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestThreadParkEvents.java b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestThreadParkEvents.java
index 6cb1b976081c..0ac39bae0408 100644
--- a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestThreadParkEvents.java
+++ b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestThreadParkEvents.java
@@ -104,6 +104,6 @@ private static void validateEvents(List<RecordedEvent> events) {
         assertTrue(parkUnparkFound);
     }
 
-    private static class Blocker {
+    private static final class Blocker {
     }
 }
diff --git a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestThreshold.java b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestThreshold.java
index 74b10fd26bf6..03f7809c86d0 100644
--- a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestThreshold.java
+++ b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/jfr/TestThreshold.java
@@ -107,7 +107,7 @@ private static void validateEvents(List<RecordedEvent> events) {
         assertTrue(foundJavaEvent && foundWaitEvent && foundParkEvent && foundSleepEvent);
     }
 
-    private static class Helper {
+    private static final class Helper {
         public synchronized void simpleWait(long millis) throws InterruptedException {
             wait(millis);
         }
diff --git a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/thread/ThreadCpuTimeTest.java b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/thread/ThreadCpuTimeTest.java
index 0dc1247bc6a0..61b0b9fcb08b 100644
--- a/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/thread/ThreadCpuTimeTest.java
+++ b/substratevm/src/com.oracle.svm.test/src/com/oracle/svm/test/thread/ThreadCpuTimeTest.java
@@ -83,7 +83,7 @@ private static long getThreadId(Thread thread) {
         return thread.getId();
     }
 
-    private class ThreadCpuTimeRunnable implements Runnable {
+    private final class ThreadCpuTimeRunnable implements Runnable {
         @Override
         public void run() {
             try {
diff --git a/substratevm/src/com.oracle.svm.truffle/src/com/oracle/svm/truffle/TruffleBaseFeature.java b/substratevm/src/com.oracle.svm.truffle/src/com/oracle/svm/truffle/TruffleBaseFeature.java
index 1ae36313f5dc..b7ecb5a9209d 100644
--- a/substratevm/src/com.oracle.svm.truffle/src/com/oracle/svm/truffle/TruffleBaseFeature.java
+++ b/substratevm/src/com.oracle.svm.truffle/src/com/oracle/svm/truffle/TruffleBaseFeature.java
@@ -1350,7 +1350,7 @@ final class Target_com_oracle_truffle_api_staticobject_ArrayBasedStaticShape {
     @Alias @RecomputeFieldValue(kind = Kind.Custom, declClass = MapCleaner.class, isFinal = true) //
     static ConcurrentHashMap<Object, Object> replacements;
 
-    private static class MapCleaner implements FieldValueTransformerWithAvailability {
+    private static final class MapCleaner implements FieldValueTransformerWithAvailability {
         @Override
         public boolean isAvailable() {
             return BuildPhaseProvider.isCompilationFinished();
@@ -1582,7 +1582,7 @@ final class Target_com_oracle_truffle_api_nodes_NodeClassImpl_NodeFieldData {
     @Alias @RecomputeFieldValue(kind = Kind.Custom, declClass = OffsetComputer.class, isFinal = true) //
     private long offset;
 
-    private static class OffsetComputer implements FieldValueTransformerWithAvailability {
+    private static final class OffsetComputer implements FieldValueTransformerWithAvailability {
         @Override
         public boolean isAvailable() {
             return BuildPhaseProvider.isHostedUniverseBuilt();
@@ -1614,7 +1614,7 @@ final class Target_com_oracle_truffle_api_dsl_InlineSupport_UnsafeField {
     @Delete private Class<?> declaringClass;
     @Delete private String name;
 
-    private static class OffsetComputer implements FieldValueTransformerWithAvailability {
+    private static final class OffsetComputer implements FieldValueTransformerWithAvailability {
         @Override
         public boolean isAvailable() {
             return BuildPhaseProvider.isHostedUniverseBuilt();
diff --git a/tools/mx.tools/suite.py b/tools/mx.tools/suite.py
index 4f3920a9ff58..d97285538874 100644
--- a/tools/mx.tools/suite.py
+++ b/tools/mx.tools/suite.py
@@ -71,7 +71,7 @@
               "com.oracle.truffle.tools.chromeinspector.instrument to org.graalvm.truffle"
             ],
             "javaCompliance" : "17+",
-            "checkstyleVersion" : "10.7.0",
+            "checkstyleVersion" : "10.21.0",
             "checkstyle" : "com.oracle.truffle.tools.chromeinspector",
             "annotationProcessors" : ["truffle:TRUFFLE_DSL_PROCESSOR"],
             "workingSets" : "Tools",
diff --git a/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/BuggyLanguageInspectDebugTest.java b/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/BuggyLanguageInspectDebugTest.java
index 04aa4b0e1246..c1bc76e2996d 100644
--- a/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/BuggyLanguageInspectDebugTest.java
+++ b/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/BuggyLanguageInspectDebugTest.java
@@ -265,7 +265,7 @@ public void verifyMessages(InspectorTester tester, int errNum) throws Interrupte
         }
     }
 
-    private static class ReadVarErrorVerifier extends ExceptionVerifier {
+    private static final class ReadVarErrorVerifier extends ExceptionVerifier {
 
         @Override
         public void verifyMessages(InspectorTester tester, int errNum) throws InterruptedException {
@@ -281,7 +281,7 @@ public void verifyMessages(InspectorTester tester, int errNum) throws Interrupte
         }
     }
 
-    private static class WriteVarErrorVerifier implements BugVerifier {
+    private static final class WriteVarErrorVerifier implements BugVerifier {
 
         @Override
         public void verifyMessages(InspectorTester tester, int errNum) throws InterruptedException {
diff --git a/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/LazyAccessInspectDebugTest.java b/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/LazyAccessInspectDebugTest.java
index e725f05d1c65..d3f06cd732c7 100644
--- a/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/LazyAccessInspectDebugTest.java
+++ b/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/LazyAccessInspectDebugTest.java
@@ -346,7 +346,7 @@ protected Object toDisplayString(boolean allowSideEffects) {
             }
         }
 
-        private static class MetaObject extends ProxyInteropObject {
+        private static final class MetaObject extends ProxyInteropObject {
 
             @Override
             protected boolean isMetaObject() {
@@ -370,7 +370,7 @@ protected String getMetaQualifiedName() throws UnsupportedMessageException {
 
         }
 
-        private static class Keys extends ProxyInteropObject {
+        private static final class Keys extends ProxyInteropObject {
 
             @Override
             protected boolean hasArrayElements() {
diff --git a/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/NotReadableValuesTest.java b/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/NotReadableValuesTest.java
index a07f844fc91e..e370bbce26c0 100644
--- a/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/NotReadableValuesTest.java
+++ b/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/NotReadableValuesTest.java
@@ -277,7 +277,7 @@ protected Object toDisplayString(boolean allowSideEffects) {
             }
         }
 
-        private static class MetaObject extends ProxyInteropObject {
+        private static final class MetaObject extends ProxyInteropObject {
 
             @Override
             protected boolean isMetaObject() {
@@ -335,7 +335,7 @@ protected Object readArrayElement(long index) throws UnsupportedMessageException
             }
         }
 
-        private static class ArrayValue extends ProxyInteropObject {
+        private static final class ArrayValue extends ProxyInteropObject {
 
             private static final long LENGTH = 6;
             private static final Set<Long> NOT_READABLE = new HashSet<>(Arrays.asList(new Long[]{2L, 3L}));
diff --git a/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/ProfilerTest.java b/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/ProfilerTest.java
index 8d62f335bc62..f6892af677c0 100644
--- a/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/ProfilerTest.java
+++ b/tools/src/com.oracle.truffle.tools.chromeinspector.test/src/com/oracle/truffle/tools/chromeinspector/test/ProfilerTest.java
@@ -108,10 +108,10 @@ public void testNoSourceCoverage() throws InterruptedException, IOException, Exe
         tester.finish();
     }
 
-    private static class TestNoSourceLanguage extends ProxyLanguage {
+    private static final class TestNoSourceLanguage extends ProxyLanguage {
 
         @Override
-        protected final CallTarget parse(TruffleLanguage.ParsingRequest request) throws Exception {
+        protected CallTarget parse(TruffleLanguage.ParsingRequest request) throws Exception {
             return new NoSourceRootNode(languageInstance).getCallTarget();
         }
 
diff --git a/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/InspectorDebugger.java b/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/InspectorDebugger.java
index 3c8d704ddd9d..d6e8a8205f2c 100644
--- a/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/InspectorDebugger.java
+++ b/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/InspectorDebugger.java
@@ -998,7 +998,7 @@ public boolean sourceMatchesBlackboxPatterns(Source source, Pattern[] patterns)
         return false;
     }
 
-    private class LoadScriptListenerImpl implements LoadScriptListener {
+    private final class LoadScriptListenerImpl implements LoadScriptListener {
 
         @Override
         public void loadedScript(Script script) {
@@ -1077,7 +1077,7 @@ private CharSequence getSourceMapURL(Source source, int lastLine) {
 
     }
 
-    private class SuspendedCallbackImpl implements SuspendedCallback {
+    private final class SuspendedCallbackImpl implements SuspendedCallback {
 
         private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1, new SchedulerThreadFactory());
         private final AtomicReference<ScheduledFuture<?>> future = new AtomicReference<>();
diff --git a/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/InspectorRuntime.java b/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/InspectorRuntime.java
index 48a5c935d3b1..b528adb7339d 100644
--- a/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/InspectorRuntime.java
+++ b/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/InspectorRuntime.java
@@ -969,7 +969,7 @@ private static String eliminateWhiteSpaces(String str) {
         return WHITESPACES_PATTERN.matcher(str).replaceAll("");
     }
 
-    private class ContextListener implements InspectorExecutionContext.Listener {
+    private final class ContextListener implements InspectorExecutionContext.Listener {
 
         @Override
         public void contextCreated(long id, String name) {
diff --git a/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/OutputHandler.java b/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/OutputHandler.java
index e7b0695d3f29..782a252bd06c 100644
--- a/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/OutputHandler.java
+++ b/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/OutputHandler.java
@@ -53,7 +53,7 @@ void setErrListener(Listener l) {
         err.l = l;
     }
 
-    private static class ListeneableOutputStream extends OutputStream {
+    private static final class ListeneableOutputStream extends OutputStream {
 
         private final CharBuffer cb = CharBuffer.allocate(8192);
         private final RBCH rbch = new RBCH();
@@ -94,7 +94,7 @@ private void wl() throws IOException {
             }
         }
 
-        private class RBCH implements ReadableByteChannel {
+        private final class RBCH implements ReadableByteChannel {
 
             private byte[] b;
             private int off;
diff --git a/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/server/InspectServerSession.java b/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/server/InspectServerSession.java
index 66816264f03a..8251ec193fd1 100644
--- a/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/server/InspectServerSession.java
+++ b/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/server/InspectServerSession.java
@@ -571,7 +571,7 @@ private static JSONObject createJsonDomain(String name) {
         return dom;
     }
 
-    private class EventHandlerImpl implements EventHandler {
+    private final class EventHandlerImpl implements EventHandler {
 
         @Override
         public void event(Event event) {
diff --git a/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/server/InspectorServer.java b/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/server/InspectorServer.java
index dd4fa49a69d9..2d6bdfd17f81 100644
--- a/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/server/InspectorServer.java
+++ b/tools/src/com.oracle.truffle.tools.chromeinspector/src/com/oracle/truffle/tools/chromeinspector/server/InspectorServer.java
@@ -234,7 +234,7 @@ public static InspectorServer get(InetSocketAddress isa, Token token, String pat
      * <li>For everything else (including missing host header), we deny the request.</li>
      * </ul>
      */
-    private class DNSRebindProtectionHandler implements Function<HttpRequest, HttpResponse> {
+    private final class DNSRebindProtectionHandler implements Function<HttpRequest, HttpResponse> {
 
         @Override
         public HttpResponse apply(HttpRequest request) {
@@ -305,7 +305,7 @@ private static String getDevtoolsAddress(String wsAddress) {
         return DEV_TOOLS_PREFIX + wsAddress.replace("://", "=");
     }
 
-    private class JSONHandler implements Function<HttpRequest, HttpResponse> {
+    private final class JSONHandler implements Function<HttpRequest, HttpResponse> {
 
         @Override
         public HttpResponse apply(HttpRequest request) {
diff --git a/tools/src/com.oracle.truffle.tools.dap/src/com/oracle/truffle/tools/dap/server/DebugProtocolServerImpl.java b/tools/src/com.oracle.truffle.tools.dap/src/com/oracle/truffle/tools/dap/server/DebugProtocolServerImpl.java
index f5c89d2b63a3..281771cb9b5f 100644
--- a/tools/src/com.oracle.truffle.tools.dap/src/com/oracle/truffle/tools/dap/server/DebugProtocolServerImpl.java
+++ b/tools/src/com.oracle.truffle.tools.dap/src/com/oracle/truffle/tools/dap/server/DebugProtocolServerImpl.java
@@ -706,7 +706,7 @@ private DebuggerSession startDebuggerSession() {
         return session;
     }
 
-    private class SuspendedCallbackImpl implements SuspendedCallback {
+    private final class SuspendedCallbackImpl implements SuspendedCallback {
 
         @Override
         public void onSuspend(SuspendedEvent event) {
@@ -756,7 +756,7 @@ public void outputText(String text) {
         }
     }
 
-    private static class AllContextsCancel implements ContextsListener {
+    private static final class AllContextsCancel implements ContextsListener {
 
         private final Phaser allClosed = new Phaser(1);
 
diff --git a/tools/src/com.oracle.truffle.tools.dap/src/com/oracle/truffle/tools/dap/server/OutputHandler.java b/tools/src/com.oracle.truffle.tools.dap/src/com/oracle/truffle/tools/dap/server/OutputHandler.java
index d3cc22385111..3ac9e0125917 100644
--- a/tools/src/com.oracle.truffle.tools.dap/src/com/oracle/truffle/tools/dap/server/OutputHandler.java
+++ b/tools/src/com.oracle.truffle.tools.dap/src/com/oracle/truffle/tools/dap/server/OutputHandler.java
@@ -53,7 +53,7 @@ void setErrListener(Listener l) {
         err.l = l;
     }
 
-    private static class ListeneableOutputStream extends OutputStream {
+    private static final class ListeneableOutputStream extends OutputStream {
 
         private final CharBuffer cb = CharBuffer.allocate(8192);
         private final RBCH rbch = new RBCH();
@@ -94,7 +94,7 @@ private void wl() throws IOException {
             }
         }
 
-        private class RBCH implements ReadableByteChannel {
+        private final class RBCH implements ReadableByteChannel {
 
             private byte[] b;
             private int off;
diff --git a/tools/src/com.oracle.truffle.tools.profiler/src/com/oracle/truffle/tools/profiler/CPUSampler.java b/tools/src/com.oracle.truffle.tools.profiler/src/com/oracle/truffle/tools/profiler/CPUSampler.java
index f9f128b4324e..7fc9679e9798 100644
--- a/tools/src/com.oracle.truffle.tools.profiler/src/com/oracle/truffle/tools/profiler/CPUSampler.java
+++ b/tools/src/com.oracle.truffle.tools.profiler/src/com/oracle/truffle/tools/profiler/CPUSampler.java
@@ -693,7 +693,7 @@ void addSelfHitTime(Long time) {
      * Process samples in a separate thread to avoid further delays during sampling and increase
      * accuracy.
      */
-    private class ResultProcessingRunnable implements Runnable {
+    private final class ResultProcessingRunnable implements Runnable {
 
         private volatile boolean cancelled;
 
@@ -806,7 +806,7 @@ static class SamplingResult {
 
     }
 
-    private class SamplingTask implements Runnable {
+    private final class SamplingTask implements Runnable {
 
         @Override
         public void run() {
diff --git a/tools/src/com.oracle.truffle.tools.profiler/src/com/oracle/truffle/tools/profiler/HeapMonitor.java b/tools/src/com.oracle.truffle.tools.profiler/src/com/oracle/truffle/tools/profiler/HeapMonitor.java
index 88abba85b0ef..4bd0a3c03fb3 100644
--- a/tools/src/com.oracle.truffle.tools.profiler/src/com/oracle/truffle/tools/profiler/HeapMonitor.java
+++ b/tools/src/com.oracle.truffle.tools.profiler/src/com/oracle/truffle/tools/profiler/HeapMonitor.java
@@ -399,7 +399,7 @@ private void cleanReferenceQueue() {
         }
     }
 
-    private class Listener implements AllocationListener {
+    private final class Listener implements AllocationListener {
 
         public void onEnter(AllocationEvent event) {
             // nothing to do
diff --git a/tools/src/org.graalvm.tools.lsp.test/src/org/graalvm/tools/lsp/test/server/LSPExtensionTestInstance.java b/tools/src/org.graalvm.tools.lsp.test/src/org/graalvm/tools/lsp/test/server/LSPExtensionTestInstance.java
index 30a961bcdecd..b7a365d295a2 100644
--- a/tools/src/org.graalvm.tools.lsp.test/src/org/graalvm/tools/lsp/test/server/LSPExtensionTestInstance.java
+++ b/tools/src/org.graalvm.tools.lsp.test/src/org/graalvm/tools/lsp/test/server/LSPExtensionTestInstance.java
@@ -48,7 +48,7 @@ protected void onCreate(Env env) {
         env.registerService(this);
     }
 
-    private static class LSPExtensionTestSimpleCommand implements LSPCommand {
+    private static final class LSPExtensionTestSimpleCommand implements LSPCommand {
 
         public String getName() {
             return COMMAND_SIMPLE;
@@ -59,7 +59,7 @@ public Object execute(LSPServerAccessor server, Env env, List<Object> arguments)
         }
     }
 
-    private static class LSPExtensionTestTimeoutCommand implements LSPCommand {
+    private static final class LSPExtensionTestTimeoutCommand implements LSPCommand {
 
         public String getName() {
             return COMMAND_TIMEOUT;
diff --git a/truffle/mx.truffle/suite.py b/truffle/mx.truffle/suite.py
index 6e1011779b22..eb9e834c9eec 100644
--- a/truffle/mx.truffle/suite.py
+++ b/truffle/mx.truffle/suite.py
@@ -233,7 +233,7 @@
         "jdk.unsupported", # sun.misc.Unsafe
       ],
       "javaCompliance" : "17+",
-      "checkstyleVersion" : "10.7.0",
+      "checkstyleVersion" : "10.21.0",
       "workingSets" : "API,Truffle",
       "javac.lint.overrides" : "none",
       "graalCompilerSourceEdition": "ignore",
@@ -588,7 +588,7 @@
       ],
       "checkstyle" : "com.oracle.truffle.dsl.processor",
       "javaCompliance" : "17+",
-      "checkstyleVersion" : "10.7.0",
+      "checkstyleVersion" : "10.21.0",
       "workingSets" : "Truffle,Codegen",
       "graalCompilerSourceEdition": "ignore",
     },
@@ -1195,7 +1195,7 @@
         "TRUFFLE_API",
       ],
       "javaCompliance" : "17+",
-      "checkstyleVersion" : "10.7.0",
+      "checkstyleVersion" : "10.21.0",
       "annotationProcessors" : ["TRUFFLE_DSL_PROCESSOR"],
       "workingSets" : "Truffle,SimpleLanguage",
       "graalCompilerSourceEdition": "ignore",
diff --git a/truffle/src/com.oracle.truffle.api.bytecode.test/src/com/oracle/truffle/api/bytecode/test/error_tests/ErrorTests.java b/truffle/src/com.oracle.truffle.api.bytecode.test/src/com/oracle/truffle/api/bytecode/test/error_tests/ErrorTests.java
index f34fa4125787..4db712d3acf7 100644
--- a/truffle/src/com.oracle.truffle.api.bytecode.test/src/com/oracle/truffle/api/bytecode/test/error_tests/ErrorTests.java
+++ b/truffle/src/com.oracle.truffle.api.bytecode.test/src/com/oracle/truffle/api/bytecode/test/error_tests/ErrorTests.java
@@ -924,10 +924,12 @@ public boolean fromInt(int x) {
         }
     }
 
+    // Checkstyle: stop
     @ExpectError("%")
     @TypeSystem
     private class ErroredTypeSystem {
     }
+    // Checkstyle: resume
 
     @ProvidedTags({RootTag.class, RootBodyTag.class})
     public class ErrorLanguage extends TruffleLanguage<Object> {
diff --git a/truffle/src/com.oracle.truffle.api.debug.test/src/com/oracle/truffle/api/debug/test/DebuggerContextsTest.java b/truffle/src/com.oracle.truffle.api.debug.test/src/com/oracle/truffle/api/debug/test/DebuggerContextsTest.java
index 2037760f7350..d6f6ac1779b7 100644
--- a/truffle/src/com.oracle.truffle.api.debug.test/src/com/oracle/truffle/api/debug/test/DebuggerContextsTest.java
+++ b/truffle/src/com.oracle.truffle.api.debug.test/src/com/oracle/truffle/api/debug/test/DebuggerContextsTest.java
@@ -256,7 +256,7 @@ public void testInContextEval() {
         }
     }
 
-    private static class TestContextsListener implements DebugContextsListener {
+    private static final class TestContextsListener implements DebugContextsListener {
 
         final List<ContextEvent> events = Collections.synchronizedList(new ArrayList<>());
 
diff --git a/truffle/src/com.oracle.truffle.api.debug.test/src/com/oracle/truffle/api/debug/test/DebuggerThreadsTest.java b/truffle/src/com.oracle.truffle.api.debug.test/src/com/oracle/truffle/api/debug/test/DebuggerThreadsTest.java
index d83a1d9c9d3b..cfc3a160f923 100644
--- a/truffle/src/com.oracle.truffle.api.debug.test/src/com/oracle/truffle/api/debug/test/DebuggerThreadsTest.java
+++ b/truffle/src/com.oracle.truffle.api.debug.test/src/com/oracle/truffle/api/debug/test/DebuggerThreadsTest.java
@@ -211,7 +211,7 @@ public void onSuspend(SuspendedEvent event) {
         }
     }
 
-    private static class TestThreadsListener implements DebugThreadsListener {
+    private static final class TestThreadsListener implements DebugThreadsListener {
 
         final List<ThreadEvent> events = Collections.synchronizedList(new ArrayList<>());
 
diff --git a/truffle/src/com.oracle.truffle.api.debug/src/com/oracle/truffle/api/debug/Breakpoint.java b/truffle/src/com.oracle.truffle.api.debug/src/com/oracle/truffle/api/debug/Breakpoint.java
index 42d51addda23..ea8851ecd21c 100644
--- a/truffle/src/com.oracle.truffle.api.debug/src/com/oracle/truffle/api/debug/Breakpoint.java
+++ b/truffle/src/com.oracle.truffle.api.debug/src/com/oracle/truffle/api/debug/Breakpoint.java
@@ -584,7 +584,7 @@ private void installInstrumentation(Instrumenter instrumenter) {
 
     // We resolve breakpoints only in sources that are executed.
     // This prevents from premature breakpoint resolution to too distant locations.
-    private class LocationsInExecutedSources implements LoadSourceSectionListener, ExecuteSourceListener {
+    private final class LocationsInExecutedSources implements LoadSourceSectionListener, ExecuteSourceListener {
 
         private final EconomicMap<Source, SourceSection> loadedSections = EconomicMap.create(Equivalence.IDENTITY_WITH_SYSTEM_HASHCODE);
         private final EconomicSet<Source> executedSources = EconomicSet.create(Equivalence.IDENTITY_WITH_SYSTEM_HASHCODE);
@@ -1248,7 +1248,7 @@ public interface ResolveListener {
         void breakpointResolved(Breakpoint breakpoint, SourceSection section);
     }
 
-    private class BreakpointNodeFactory implements ExecutionEventNodeFactory {
+    private final class BreakpointNodeFactory implements ExecutionEventNodeFactory {
 
         @Override
         public ExecutionEventNode create(EventContext context) {
diff --git a/truffle/src/com.oracle.truffle.api.debug/src/com/oracle/truffle/api/debug/SuspendedEvent.java b/truffle/src/com.oracle.truffle.api.debug/src/com/oracle/truffle/api/debug/SuspendedEvent.java
index 9bc64574f718..911d13dd9144 100644
--- a/truffle/src/com.oracle.truffle.api.debug/src/com/oracle/truffle/api/debug/SuspendedEvent.java
+++ b/truffle/src/com.oracle.truffle.api.debug/src/com/oracle/truffle/api/debug/SuspendedEvent.java
@@ -1069,7 +1069,7 @@ private static List<DebugStackTraceElement> getAsynchronousStackFrames(DebuggerS
         }
 
         // This implementation prevents from calling size()
-        private class Itr implements Iterator<List<DebugStackTraceElement>> {
+        private final class Itr implements Iterator<List<DebugStackTraceElement>> {
             int cursor = 0;
 
             @Override
diff --git a/truffle/src/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/FallbackTest.java b/truffle/src/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/FallbackTest.java
index 66c5319b4871..8807c0a8657b 100644
--- a/truffle/src/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/FallbackTest.java
+++ b/truffle/src/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/FallbackTest.java
@@ -263,7 +263,7 @@ public void testFallback6() {
     }
 
     @SuppressWarnings("serial")
-    private static class FallbackException extends RuntimeException {
+    private static final class FallbackException extends RuntimeException {
     }
 
     @NodeChild("a")
diff --git a/truffle/src/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/ImportGuardsTest.java b/truffle/src/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/ImportGuardsTest.java
index 9c14f4104304..42beaf7a306b 100644
--- a/truffle/src/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/ImportGuardsTest.java
+++ b/truffle/src/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/ImportGuardsTest.java
@@ -148,7 +148,7 @@ int do1(int a) {
         }
     }
 
-    private static class Imports2 {
+    private static final class Imports2 {
 
     }
 
diff --git a/truffle/src/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/NodeChildNoNameTest.java b/truffle/src/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/NodeChildNoNameTest.java
index 7aab33ab81a8..5ade745e9222 100644
--- a/truffle/src/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/NodeChildNoNameTest.java
+++ b/truffle/src/com.oracle.truffle.api.dsl.test/src/com/oracle/truffle/api/dsl/test/NodeChildNoNameTest.java
@@ -84,7 +84,7 @@ public void testThreeArg() {
         Assert.assertEquals(126, TestHelper.createCallTarget(arg).call());
     }
 
-    private static class ConstantNode extends ValueNode {
+    private static final class ConstantNode extends ValueNode {
 
         @Override
         public Object execute(VirtualFrame frame) {
diff --git a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/GenerateWrapperTest.java b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/GenerateWrapperTest.java
index cad81af599cf..da0b33b3aec3 100644
--- a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/GenerateWrapperTest.java
+++ b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/GenerateWrapperTest.java
@@ -1023,7 +1023,7 @@ public boolean isInstrumentable() {
 
     @ExpectError("Class must not be private to generate a wrapper.")
     @GenerateWrapper
-    private static class ErrorNode2 extends Node implements InstrumentableNode {
+    private static final class ErrorNode2 extends Node implements InstrumentableNode {
 
         public WrapperNode createWrapper(ProbeNode probe) {
             return null;
diff --git a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/InstrumentationNoExceptionsTest.java b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/InstrumentationNoExceptionsTest.java
index 1f9d6bebf032..512e994c74cc 100644
--- a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/InstrumentationNoExceptionsTest.java
+++ b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/InstrumentationNoExceptionsTest.java
@@ -440,7 +440,7 @@ public void onReturnExceptional(EventContext ctx, VirtualFrame frame, Throwable
     }
 
     @SuppressWarnings("serial")
-    private static class MyInstrumentException extends RuntimeException {
+    private static final class MyInstrumentException extends RuntimeException {
     }
 
 }
diff --git a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/InstrumentationTest.java b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/InstrumentationTest.java
index 233de683eb16..cac3897c0906 100644
--- a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/InstrumentationTest.java
+++ b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/InstrumentationTest.java
@@ -367,7 +367,7 @@ public void testLanguageInstrumentationAndExceptions() throws IOException {
     }
 
     @SuppressWarnings("serial")
-    private static class MyLanguageException extends RuntimeException {
+    private static final class MyLanguageException extends RuntimeException {
 
     }
 
@@ -1384,7 +1384,7 @@ public void testUsedTagNotRequired1() throws IOException {
     @Registration(id = "testUsedTagNotRequired1", services = Object.class)
     public static class TestUsedTagNotRequired1 extends TruffleInstrument {
 
-        private static class Foobar {
+        private static final class Foobar {
 
         }
 
diff --git a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/InstrumentationTestLanguage.java b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/InstrumentationTestLanguage.java
index 7bc0a6880e42..dcb3c21af026 100644
--- a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/InstrumentationTestLanguage.java
+++ b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/InstrumentationTestLanguage.java
@@ -3780,7 +3780,7 @@ Object getMetaObject() {
 
     }
 
-    private static class StringBuilderWrapper {
+    private static final class StringBuilderWrapper {
         private final StringBuilder delegate = new StringBuilder();
 
         @TruffleBoundary
@@ -3857,7 +3857,7 @@ static InstrumentContext get(Node node) {
         return REFERENCE.get(node);
     }
 
-    private static class WeakSet<T> extends AbstractSet<T> {
+    private static final class WeakSet<T> extends AbstractSet<T> {
 
         private final Map<T, Void> map = new WeakHashMap<>();
 
diff --git a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/SourceListenerTest.java b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/SourceListenerTest.java
index b77b6c49f1b6..64ef7cb6433f 100644
--- a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/SourceListenerTest.java
+++ b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/SourceListenerTest.java
@@ -393,7 +393,7 @@ public void testLoadSourceException() throws IOException {
         }
     }
 
-    private static class TestLoadSourceExceptionClass extends RuntimeException {
+    private static final class TestLoadSourceExceptionClass extends RuntimeException {
 
         private static final long serialVersionUID = 1L;
 
diff --git a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/SourceSectionListenerTest.java b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/SourceSectionListenerTest.java
index eada11ae12d2..f383d66efce2 100644
--- a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/SourceSectionListenerTest.java
+++ b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/SourceSectionListenerTest.java
@@ -373,7 +373,7 @@ public void onReturnExceptional(EventContext c, VirtualFrame frame, Throwable ex
         }
     };
 
-    private static class TestLoadSourceSectionExceptionClass extends RuntimeException {
+    private static final class TestLoadSourceSectionExceptionClass extends RuntimeException {
 
         private static final long serialVersionUID = 1L;
 
diff --git a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/TagsTest.java b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/TagsTest.java
index f48fadcd27b1..9d22576d9bb4 100644
--- a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/TagsTest.java
+++ b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/TagsTest.java
@@ -82,12 +82,12 @@
 
 public class TagsTest {
 
-    private static class MyTag extends Tag {
+    private static final class MyTag extends Tag {
 
     }
 
     @Tag.Identifier("MyTagWithIdentifier")
-    private static class MyTagWithIdentifier extends Tag {
+    private static final class MyTagWithIdentifier extends Tag {
 
     }
 
diff --git a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/VariablesScopeTest.java b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/VariablesScopeTest.java
index 0870a80d28a1..3e128687ad07 100644
--- a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/VariablesScopeTest.java
+++ b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/VariablesScopeTest.java
@@ -194,7 +194,7 @@ private static boolean isNull(Object object) {
         return INTEROP.isNull(object);
     }
 
-    private static class ILScopeTester implements TestScopeInstrument.Tester {
+    private static final class ILScopeTester implements TestScopeInstrument.Tester {
 
         public void doTestScope(TruffleInstrument.Env env, Node node, VirtualFrame frame, boolean nodeEnter) throws Exception {
             assertTrue(NodeLibrary.getUncached().hasScope(node, null));
@@ -261,7 +261,7 @@ private static void doTestTopScope(TruffleInstrument.Env env) throws Unsupported
         }
     }
 
-    private static class DefaultScopeTester implements TestScopeInstrument.Tester {
+    private static final class DefaultScopeTester implements TestScopeInstrument.Tester {
 
         private final StringBuilder visitedLocations = new StringBuilder();
 
@@ -620,7 +620,7 @@ final Object getScope(Frame frame, @SuppressWarnings("unused") boolean nodeEnter
         }
     }
 
-    private static class CustomScopeTester implements TestScopeInstrument.Tester {
+    private static final class CustomScopeTester implements TestScopeInstrument.Tester {
 
         @Override
         public void doTestScope(TruffleInstrument.Env env, Node node, VirtualFrame frame, boolean nodeEnter) {
diff --git a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/examples/DebuggerExample.java b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/examples/DebuggerExample.java
index 3dd99eb0535d..00d571bc80c4 100644
--- a/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/examples/DebuggerExample.java
+++ b/truffle/src/com.oracle.truffle.api.instrumentation.test/src/com/oracle/truffle/api/instrumentation/test/examples/DebuggerExample.java
@@ -172,7 +172,7 @@ public void onReturnExceptional(EventContext context, VirtualFrame frame, Throwa
             }
         }
 
-        private class Stepping implements ExecutionEventListener {
+        private final class Stepping implements ExecutionEventListener {
 
             public void onEnter(EventContext context, VirtualFrame frame) {
                 ontStatementStep(context);
diff --git a/truffle/src/com.oracle.truffle.api.instrumentation/src/com/oracle/truffle/api/instrumentation/AllocationReporter.java b/truffle/src/com.oracle.truffle.api.instrumentation/src/com/oracle/truffle/api/instrumentation/AllocationReporter.java
index f01f61faa000..acda7a690da5 100644
--- a/truffle/src/com.oracle.truffle.api.instrumentation/src/com/oracle/truffle/api/instrumentation/AllocationReporter.java
+++ b/truffle/src/com.oracle.truffle.api.instrumentation/src/com/oracle/truffle/api/instrumentation/AllocationReporter.java
@@ -418,7 +418,7 @@ private static Object createComplexObject() {
         return null;
     }
 
-    private static class MyTruffleObject {
+    private static final class MyTruffleObject {
     }
 
 }
diff --git a/truffle/src/com.oracle.truffle.api.instrumentation/src/com/oracle/truffle/api/instrumentation/InstrumentationHandler.java b/truffle/src/com.oracle.truffle.api.instrumentation/src/com/oracle/truffle/api/instrumentation/InstrumentationHandler.java
index 2e492d2006f8..aa9a398d3386 100644
--- a/truffle/src/com.oracle.truffle.api.instrumentation/src/com/oracle/truffle/api/instrumentation/InstrumentationHandler.java
+++ b/truffle/src/com.oracle.truffle.api.instrumentation/src/com/oracle/truffle/api/instrumentation/InstrumentationHandler.java
@@ -1689,7 +1689,7 @@ protected void postVisitNotifications(Set<Class<?>> providedTags, SourceSection
      * visitorBuilder.buildVisitor();
      * </pre>
      */
-    private class VisitorBuilder {
+    private final class VisitorBuilder {
         List<VisitOperation> operations = new ArrayList<>();
         boolean shouldMaterializeSyntaxNodes;
 
diff --git a/truffle/src/com.oracle.truffle.api.library.test/src/com/oracle/truffle/api/library/test/ExportLibraryTest.java b/truffle/src/com.oracle.truffle.api.library.test/src/com/oracle/truffle/api/library/test/ExportLibraryTest.java
index aa754b936856..0ae0ebe8638c 100644
--- a/truffle/src/com.oracle.truffle.api.library.test/src/com/oracle/truffle/api/library/test/ExportLibraryTest.java
+++ b/truffle/src/com.oracle.truffle.api.library.test/src/com/oracle/truffle/api/library/test/ExportLibraryTest.java
@@ -181,10 +181,10 @@ static class ExportsTestObjectError1 {
 
     @ExportLibrary(ExportLibraryTestLibrary.class)
     @ExpectError("The exported type must not be private. Increase visibility to resolve this.")
-    private static class ExportsTestObjectError2 {
+    private static final class ExportsTestObjectError2 {
         @SuppressWarnings("static-method")
         @ExportMessage
-        final Object m0() {
+        Object m0() {
             return null;
         }
     }
@@ -213,7 +213,7 @@ private Object m0(@SuppressWarnings("unused") @Cached("null") Object foo) {
     static class ExportsTestObjectError5 {
         @ExpectError("Exported message node class must not be private.")
         @ExportMessage
-        private static class M0 {
+        private static final class M0 {
         }
     }
 
diff --git a/truffle/src/com.oracle.truffle.api.library.test/src/com/oracle/truffle/api/library/test/ExportMethodTest.java b/truffle/src/com.oracle.truffle.api.library.test/src/com/oracle/truffle/api/library/test/ExportMethodTest.java
index 2c1a22237095..0deead504285 100644
--- a/truffle/src/com.oracle.truffle.api.library.test/src/com/oracle/truffle/api/library/test/ExportMethodTest.java
+++ b/truffle/src/com.oracle.truffle.api.library.test/src/com/oracle/truffle/api/library/test/ExportMethodTest.java
@@ -153,11 +153,11 @@ public void test() {
         assertEquals("foo", getUncached(ExportsTestLibrary1.class, o).foo(o, 42));
     }
 
-    private static class TestSubInterface implements TestInterface {
+    private static final class TestSubInterface implements TestInterface {
 
     }
 
-    private static class TestSubClass extends TestClass {
+    private static final class TestSubClass extends TestClass {
 
     }
 
diff --git a/truffle/src/com.oracle.truffle.api.library.test/src/com/oracle/truffle/api/library/test/ExportNodeTest.java b/truffle/src/com.oracle.truffle.api.library.test/src/com/oracle/truffle/api/library/test/ExportNodeTest.java
index 456bc0e99a17..20c9e0959545 100644
--- a/truffle/src/com.oracle.truffle.api.library.test/src/com/oracle/truffle/api/library/test/ExportNodeTest.java
+++ b/truffle/src/com.oracle.truffle.api.library.test/src/com/oracle/truffle/api/library/test/ExportNodeTest.java
@@ -551,7 +551,7 @@ static class TestObjectError3 {
 
         @ExportMessage
         @ExpectError("Exported message node class must not be private.")
-        private static class Foo {
+        private static final class Foo {
 
             static Foo create() {
                 return null;
diff --git a/truffle/src/com.oracle.truffle.api.staticobject.test/src/com/oracle/truffle/api/staticobject/test/VisibilityTest.java b/truffle/src/com.oracle.truffle.api.staticobject.test/src/com/oracle/truffle/api/staticobject/test/VisibilityTest.java
index f43cd4ce3c97..bdb3907cbcd3 100644
--- a/truffle/src/com.oracle.truffle.api.staticobject.test/src/com/oracle/truffle/api/staticobject/test/VisibilityTest.java
+++ b/truffle/src/com.oracle.truffle.api.staticobject.test/src/com/oracle/truffle/api/staticobject/test/VisibilityTest.java
@@ -46,7 +46,7 @@ static Class<?> getPrivateClass() {
         return PrivateClass.class;
     }
 
-    private static class PrivateClass {
+    private static final class PrivateClass {
 
     }
 }
diff --git a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/host/PrimitiveRawArrayInteropTest.java b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/host/PrimitiveRawArrayInteropTest.java
index 9692f0f5dc0d..edbf2925b212 100644
--- a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/host/PrimitiveRawArrayInteropTest.java
+++ b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/host/PrimitiveRawArrayInteropTest.java
@@ -288,7 +288,7 @@ private static void assertSum(String msg, double expected, List<? extends Object
         assertEquals(msg, expected, v, 0.05);
     }
 
-    private static class SimulatedDeath extends ThreadDeath {
+    private static final class SimulatedDeath extends ThreadDeath {
         private static final long serialVersionUID = 1L;
 
         @Override
diff --git a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/host/SeparateClassloaderTestRunner.java b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/host/SeparateClassloaderTestRunner.java
index 110079f24f4a..c0c083fc0eeb 100644
--- a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/host/SeparateClassloaderTestRunner.java
+++ b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/host/SeparateClassloaderTestRunner.java
@@ -73,7 +73,7 @@ public Theories(Class<?> clazz) throws InitializationError {
      * As of JDK9, Truffle API is deployed in a module (possibly the unnamed module) so to retrieve
      * the class file bytes for separate class loading requires using module API.
      */
-    private static class JDK9TestClassLoader extends ClassLoader {
+    private static final class JDK9TestClassLoader extends ClassLoader {
 
         @Override
         public Class<?> loadClass(String name) throws ClassNotFoundException {
diff --git a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/nodes/EncapsulatedNodeTest.java b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/nodes/EncapsulatedNodeTest.java
index e1093fe183c8..6579237e373a 100644
--- a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/nodes/EncapsulatedNodeTest.java
+++ b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/nodes/EncapsulatedNodeTest.java
@@ -293,7 +293,7 @@ private static List<TruffleStackTraceElement> captureStackLazily() {
     }
 
     @SuppressWarnings("serial")
-    private static class GetStackTraceException extends AbstractTruffleException {
+    private static final class GetStackTraceException extends AbstractTruffleException {
     }
 
     @TruffleBoundary
diff --git a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/nodes/NodeUtilTest.java b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/nodes/NodeUtilTest.java
index a6ecd86f2f70..e7a576da0396 100644
--- a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/nodes/NodeUtilTest.java
+++ b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/nodes/NodeUtilTest.java
@@ -86,7 +86,7 @@ public void testAssertNotAdopted() {
         });
     }
 
-    private static class NotAdoptableNode extends Node {
+    private static final class NotAdoptableNode extends Node {
         @Override
         public boolean isAdoptable() {
             return false;
diff --git a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/nodes/SafeReplaceTest.java b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/nodes/SafeReplaceTest.java
index 727fb2befe21..76ed4b5c4d2d 100644
--- a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/nodes/SafeReplaceTest.java
+++ b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/nodes/SafeReplaceTest.java
@@ -93,7 +93,7 @@ public void testIncorrectReplacement() {
         assertFalse(oldChild.isSafelyReplaceableBy(wrongTypeNewChild));
     }
 
-    private static class TestNode extends Node {
+    private static final class TestNode extends Node {
 
         private int executed;
 
@@ -121,7 +121,7 @@ public Object execute(VirtualFrame frame) {
         }
     }
 
-    private static class WrongTestNode extends Node {
+    private static final class WrongTestNode extends Node {
     }
 
 }
diff --git a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ByteSequenceTest.java b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ByteSequenceTest.java
index 3ee2a11994c3..ad47a4d1a65e 100644
--- a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ByteSequenceTest.java
+++ b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ByteSequenceTest.java
@@ -55,7 +55,7 @@
 
 public class ByteSequenceTest {
 
-    private static class ByteSequenceImpl implements ByteSequence {
+    private static final class ByteSequenceImpl implements ByteSequence {
 
         public int length() {
             return 4;
diff --git a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/GR43906Test.java b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/GR43906Test.java
index 097417a1b8b8..f9ff4c20fee0 100644
--- a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/GR43906Test.java
+++ b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/GR43906Test.java
@@ -75,7 +75,7 @@ protected Object execute(RootNode node, Env env, Object[] contextArguments, Obje
         }
     }
 
-    private static class DummyOutputStream extends OutputStream {
+    private static final class DummyOutputStream extends OutputStream {
         private int i = 0;
         private int length = 0;
 
diff --git a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/MessageTransportTest.java b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/MessageTransportTest.java
index eedce6042460..73678d8e23b1 100644
--- a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/MessageTransportTest.java
+++ b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/MessageTransportTest.java
@@ -204,7 +204,7 @@ private enum MessageKind {
         CLOSE
     }
 
-    private static class MessageHandlerVerifier implements MessageEndpoint {
+    private static final class MessageHandlerVerifier implements MessageEndpoint {
 
         private MessageKind expectedKind;
         private String expectedText;
diff --git a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ProcessBuilderTest.java b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ProcessBuilderTest.java
index 57f2da868067..8232cdbb1408 100644
--- a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ProcessBuilderTest.java
+++ b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ProcessBuilderTest.java
@@ -555,7 +555,7 @@ private static Map<String, String> pairsAsMap(String... keyValuePairs) {
         return map;
     }
 
-    private static class MockProcessHandler implements ProcessHandler {
+    private static final class MockProcessHandler implements ProcessHandler {
 
         private ProcessCommand lastCommand;
 
diff --git a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ProxySPITest.java b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ProxySPITest.java
index 09d19b06a6aa..375c853b52cd 100644
--- a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ProxySPITest.java
+++ b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ProxySPITest.java
@@ -820,7 +820,7 @@ static class TestError extends RuntimeException {
     }
 
     @SuppressWarnings("deprecation")
-    private static class AllProxy implements ProxyArray, ProxyObject, ProxyNativeObject, ProxyExecutable, ProxyInstantiable {
+    private static final class AllProxy implements ProxyArray, ProxyObject, ProxyNativeObject, ProxyExecutable, ProxyInstantiable {
 
         public Object execute(Value... t) {
             throw new TestError();
diff --git a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ValueAPITest.java b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ValueAPITest.java
index 23c569cfc15e..9aa6380a9170 100644
--- a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ValueAPITest.java
+++ b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ValueAPITest.java
@@ -1041,7 +1041,7 @@ private static <T> void objectCoercionTest(Object value, Class<T> expectedType,
         }
     }
 
-    private static class DummyList extends DummyCollection implements List<Object> {
+    private static final class DummyList extends DummyCollection implements List<Object> {
 
         public boolean addAll(int index, Collection<? extends Object> c) {
             return values.addAll(index, c);
@@ -1150,13 +1150,13 @@ public <T> Object coerce(T value, Consumer<T> o) {
 
     }
 
-    public static class EmptyObject {
+    public static final class EmptyObject {
     }
 
-    private static class PrivateObject {
+    private static final class PrivateObject {
     }
 
-    private static class FieldAccess {
+    private static final class FieldAccess {
         @SuppressWarnings("unused") public EmptyObject member;
     }
 
@@ -1332,7 +1332,7 @@ public long getSize() {
 
     }
 
-    private static class MembersAndExecutable extends Members implements ProxyObject, ProxyExecutable {
+    private static final class MembersAndExecutable extends Members implements ProxyObject, ProxyExecutable {
 
         Object executableResult;
 
@@ -1341,7 +1341,7 @@ public Object execute(Value... arguments) {
         }
     }
 
-    private static class MembersAndInstantiable extends Members implements ProxyObject, ProxyInstantiable {
+    private static final class MembersAndInstantiable extends Members implements ProxyObject, ProxyInstantiable {
 
         Object instantiableResult;
 
@@ -1351,7 +1351,7 @@ public Object newInstance(Value... arguments) {
 
     }
 
-    private static class MembersAndArrayAndExecutable extends MembersAndArray implements ProxyArray, ProxyObject, ProxyExecutable {
+    private static final class MembersAndArrayAndExecutable extends MembersAndArray implements ProxyArray, ProxyObject, ProxyExecutable {
 
         Object executableResult;
 
@@ -1361,7 +1361,7 @@ public Object execute(Value... arguments) {
 
     }
 
-    private static class MembersAndArrayAndInstantiable extends MembersAndArray implements ProxyArray, ProxyObject, ProxyInstantiable {
+    private static final class MembersAndArrayAndInstantiable extends MembersAndArray implements ProxyArray, ProxyObject, ProxyInstantiable {
 
         Object instantiableResult;
 
@@ -1371,7 +1371,7 @@ public Object newInstance(Value... arguments) {
 
     }
 
-    private static class MembersAndArrayAndExecutableAndInstantiable extends MembersAndArray implements ProxyArray, ProxyObject, ProxyInstantiable, ProxyExecutable {
+    private static final class MembersAndArrayAndExecutableAndInstantiable extends MembersAndArray implements ProxyArray, ProxyObject, ProxyInstantiable, ProxyExecutable {
 
         Object executableResult;
         Object instantiableResult;
@@ -1386,7 +1386,7 @@ public Object newInstance(Value... arguments) {
 
     }
 
-    private static class Executable implements ProxyExecutable {
+    private static final class Executable implements ProxyExecutable {
 
         Object executableResult;
 
@@ -1591,7 +1591,7 @@ public void testPrimitiveCoercionErrors() {
 
     }
 
-    private static class EmptyProxy implements org.graalvm.polyglot.proxy.Proxy {
+    private static final class EmptyProxy implements org.graalvm.polyglot.proxy.Proxy {
 
         @Override
         public String toString() {
diff --git a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ValueHostConversionTest.java b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ValueHostConversionTest.java
index 8a1e74b456de..920b7a8840a7 100644
--- a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ValueHostConversionTest.java
+++ b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/polyglot/ValueHostConversionTest.java
@@ -198,7 +198,7 @@ public interface SupplierExtension extends Supplier<Integer> {
         Integer get();
     }
 
-    private class SuplierExtensionImpl implements SupplierExtension {
+    private final class SuplierExtensionImpl implements SupplierExtension {
         @Override
         public Integer get() {
             return 42;
diff --git a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/profiles/ExactClassValueProfileTest.java b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/profiles/ExactClassValueProfileTest.java
index 6787698e18f3..a4f9ca4c854a 100644
--- a/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/profiles/ExactClassValueProfileTest.java
+++ b/truffle/src/com.oracle.truffle.api.test/src/com/oracle/truffle/api/test/profiles/ExactClassValueProfileTest.java
@@ -61,7 +61,7 @@ public class ExactClassValueProfileTest extends AbstractProfileTest {
     private static class TestBaseClass {
     }
 
-    private static class TestSubClass extends TestBaseClass {
+    private static final class TestSubClass extends TestBaseClass {
     }
 
     @BeforeClass
diff --git a/truffle/src/com.oracle.truffle.api/src/com/oracle/truffle/api/impl/Accessor.java b/truffle/src/com.oracle.truffle.api/src/com/oracle/truffle/api/impl/Accessor.java
index 660a04485110..328a19fadd32 100644
--- a/truffle/src/com.oracle.truffle.api/src/com/oracle/truffle/api/impl/Accessor.java
+++ b/truffle/src/com.oracle.truffle.api/src/com/oracle/truffle/api/impl/Accessor.java
@@ -1462,7 +1462,7 @@ public final void startOSRFrameTransfer(FrameWithoutBoxing target) {
 
 // A separate class to break the cycle such that Accessor can fully initialize
 // before ...Accessor classes static initializers run, which call methods from Accessor.
-    private static class Constants {
+    private static final class Constants {
 
         private static final Accessor.LanguageSupport LANGUAGE;
         private static final Accessor.NodeSupport NODES;
diff --git a/truffle/src/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/java/ElementUtils.java b/truffle/src/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/java/ElementUtils.java
index 8c37d6579b8c..e3e3585995a6 100644
--- a/truffle/src/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/java/ElementUtils.java
+++ b/truffle/src/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/java/ElementUtils.java
@@ -1303,7 +1303,7 @@ public static Object unboxAnnotationValue(AnnotationValue value) {
         return value.accept(new AnnotationValueVisitorImpl(), null);
     }
 
-    private static class AnnotationValueVisitorImpl extends AbstractAnnotationValueVisitor8<Object, Void> {
+    private static final class AnnotationValueVisitorImpl extends AbstractAnnotationValueVisitor8<Object, Void> {
 
         @Override
         public Object visitBoolean(boolean b, Void p) {
diff --git a/truffle/src/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/java/transform/OrganizedImports.java b/truffle/src/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/java/transform/OrganizedImports.java
index cdfa0e84eb37..0d8918758974 100644
--- a/truffle/src/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/java/transform/OrganizedImports.java
+++ b/truffle/src/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/java/transform/OrganizedImports.java
@@ -497,7 +497,7 @@ public void visitImport(CodeImport e, Void p) {
 
     }
 
-    private class ImportTypeReferenceVisitor extends TypeReferenceVisitor {
+    private final class ImportTypeReferenceVisitor extends TypeReferenceVisitor {
 
         @Override
         public void visitStaticFieldReference(Element enclosedType, TypeMirror type, String elementName) {
diff --git a/truffle/src/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/parser/NodeParser.java b/truffle/src/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/parser/NodeParser.java
index 56e5e7af0561..2be7d62384c2 100644
--- a/truffle/src/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/parser/NodeParser.java
+++ b/truffle/src/com.oracle.truffle.dsl.processor/src/com/oracle/truffle/dsl/processor/parser/NodeParser.java
@@ -4263,7 +4263,7 @@ private static boolean isRecursiveType(NodeData node, TypeElement parameterType)
 
     private final Map<String, NodeData> nodeDataCache = new HashMap<>();
 
-    private static class FactoryMethodCacheKey {
+    private static final class FactoryMethodCacheKey {
     }
 
     private List<CodeExecutableElement> parseNodeFactoryMethods(TypeMirror nodeType) {
@@ -4911,7 +4911,7 @@ public int hashCode() {
             return hashCode;
         }
 
-        private static class DSLExpressionHash implements DSLExpressionVisitor {
+        private static final class DSLExpressionHash implements DSLExpressionVisitor {
             private int hash = 1;
 
             public void visitCast(Cast binary) {
diff --git a/truffle/src/com.oracle.truffle.nfi.backend.libffi/src/com/oracle/truffle/nfi/backend/libffi/LibFFIContext.java b/truffle/src/com.oracle.truffle.nfi.backend.libffi/src/com/oracle/truffle/nfi/backend/libffi/LibFFIContext.java
index cfeb45172957..aed5dc57b90c 100644
--- a/truffle/src/com.oracle.truffle.nfi.backend.libffi/src/com/oracle/truffle/nfi/backend/libffi/LibFFIContext.java
+++ b/truffle/src/com.oracle.truffle.nfi.backend.libffi/src/com/oracle/truffle/nfi/backend/libffi/LibFFIContext.java
@@ -113,7 +113,7 @@ public void destroy() {
         }
     }
 
-    private class NativeEnvSupplier implements Supplier<NativeEnv> {
+    private final class NativeEnvSupplier implements Supplier<NativeEnv> {
 
         @Override
         public NativeEnv get() {
diff --git a/truffle/src/com.oracle.truffle.nfi.test/src/com/oracle/truffle/nfi/test/WrappedPrimitiveNFITest.java b/truffle/src/com.oracle.truffle.nfi.test/src/com/oracle/truffle/nfi/test/WrappedPrimitiveNFITest.java
index fb5ffed1c36b..13db97ae1bdb 100644
--- a/truffle/src/com.oracle.truffle.nfi.test/src/com/oracle/truffle/nfi/test/WrappedPrimitiveNFITest.java
+++ b/truffle/src/com.oracle.truffle.nfi.test/src/com/oracle/truffle/nfi/test/WrappedPrimitiveNFITest.java
@@ -59,7 +59,7 @@
 @Parameterized.UseParametersRunnerFactory(TruffleRunner.ParametersFactory.class)
 public class WrappedPrimitiveNFITest extends NFITest {
 
-    private static class TestObject implements TruffleObject {
+    private static final class TestObject implements TruffleObject {
     }
 
     private static final Object[] ARGUMENTS = {
diff --git a/truffle/src/com.oracle.truffle.polyglot/src/com/oracle/truffle/polyglot/PolyglotLanguageContext.java b/truffle/src/com.oracle.truffle.polyglot/src/com/oracle/truffle/polyglot/PolyglotLanguageContext.java
index bff7d5f507f4..2126c8a91ede 100644
--- a/truffle/src/com.oracle.truffle.polyglot/src/com/oracle/truffle/polyglot/PolyglotLanguageContext.java
+++ b/truffle/src/com.oracle.truffle.polyglot/src/com/oracle/truffle/polyglot/PolyglotLanguageContext.java
@@ -1094,7 +1094,7 @@ public String toString() {
         return "PolyglotLanguageContext [language=" + language + ", initialized=" + (env != null) + "]";
     }
 
-    private class PolyglotUncaughtExceptionHandler implements Thread.UncaughtExceptionHandler {
+    private final class PolyglotUncaughtExceptionHandler implements Thread.UncaughtExceptionHandler {
 
         @SuppressWarnings({"unused", "try"})
         @Override
diff --git a/truffle/src/com.oracle.truffle.sl.test/src/com/oracle/truffle/sl/test/SLInstrumentTest.java b/truffle/src/com.oracle.truffle.sl.test/src/com/oracle/truffle/sl/test/SLInstrumentTest.java
index 31eb86c1bb73..a04bc42fbaf8 100644
--- a/truffle/src/com.oracle.truffle.sl.test/src/com/oracle/truffle/sl/test/SLInstrumentTest.java
+++ b/truffle/src/com.oracle.truffle.sl.test/src/com/oracle/truffle/sl/test/SLInstrumentTest.java
@@ -660,7 +660,7 @@ public int read() throws IOException {
         assertFalse(redoIO.beforePop);
     }
 
-    private static class RuntimeInterruptedException extends AbstractTruffleException {
+    private static final class RuntimeInterruptedException extends AbstractTruffleException {
         private static final long serialVersionUID = -4735601164894088571L;
     }
 
diff --git a/truffle/src/com.oracle.truffle.sl.test/src/com/oracle/truffle/sl/test/SLInteropObjectTest.java b/truffle/src/com.oracle.truffle.sl.test/src/com/oracle/truffle/sl/test/SLInteropObjectTest.java
index 3f86b6d54309..dc63363c7f74 100644
--- a/truffle/src/com.oracle.truffle.sl.test/src/com/oracle/truffle/sl/test/SLInteropObjectTest.java
+++ b/truffle/src/com.oracle.truffle.sl.test/src/com/oracle/truffle/sl/test/SLInteropObjectTest.java
@@ -100,7 +100,7 @@ public void testNewForeign() {
         Assert.assertEquals(20, ret.asLong());
     }
 
-    private static class TestType implements ProxyInstantiable {
+    private static final class TestType implements ProxyInstantiable {
 
         @Override
         public Object newInstance(Value... arguments) {
@@ -109,7 +109,7 @@ public Object newInstance(Value... arguments) {
 
     }
 
-    private static class TestObject implements ProxyObject {
+    private static final class TestObject implements ProxyObject {
 
         private long value;
 
diff --git a/truffle/src/com.oracle.truffle.sl/src/com/oracle/truffle/sl/parser/SLBaseParser.java b/truffle/src/com.oracle.truffle.sl/src/com/oracle/truffle/sl/parser/SLBaseParser.java
index 06591120aa38..49ed5b627c92 100644
--- a/truffle/src/com.oracle.truffle.sl/src/com/oracle/truffle/sl/parser/SLBaseParser.java
+++ b/truffle/src/com.oracle.truffle.sl/src/com/oracle/truffle/sl/parser/SLBaseParser.java
@@ -133,7 +133,7 @@ protected TruffleString asTruffleString(Token literalToken, boolean removeQuotes
 
     // ------------------------------- locals handling --------------------------
 
-    private static class FindLocalsVisitor extends SimpleLanguageBaseVisitor<Void> {
+    private static final class FindLocalsVisitor extends SimpleLanguageBaseVisitor<Void> {
         boolean entered = false;
         List<Token> results = new ArrayList<>();
 
diff --git a/truffle/src/com.oracle.truffle.sl/src/com/oracle/truffle/sl/parser/SLNodeParser.java b/truffle/src/com.oracle.truffle.sl/src/com/oracle/truffle/sl/parser/SLNodeParser.java
index ff71591cc0cd..7cca3ed910f9 100644
--- a/truffle/src/com.oracle.truffle.sl/src/com/oracle/truffle/sl/parser/SLNodeParser.java
+++ b/truffle/src/com.oracle.truffle.sl/src/com/oracle/truffle/sl/parser/SLNodeParser.java
@@ -192,7 +192,7 @@ private SLStringLiteralNode createString(Token name, boolean removeQuotes) {
         return node;
     }
 
-    private class SLStatementVisitor extends SimpleLanguageBaseVisitor<SLStatementNode> {
+    private final class SLStatementVisitor extends SimpleLanguageBaseVisitor<SLStatementNode> {
         @Override
         public SLStatementNode visitBlock(BlockContext ctx) {
             List<TruffleString> newLocals = enterBlock(ctx);
@@ -326,7 +326,7 @@ public SLStatementNode visitChildren(RuleNode arg0) {
         }
     }
 
-    private class SLExpressionVisitor extends SimpleLanguageBaseVisitor<SLExpressionNode> {
+    private final class SLExpressionVisitor extends SimpleLanguageBaseVisitor<SLExpressionNode> {
         @Override
         public SLExpressionNode visitExpression(ExpressionContext ctx) {
             return createBinary(ctx.logic_term(), ctx.OP_OR());
diff --git a/truffle/src/com.oracle.truffle.tck.instrumentation/src/com/oracle/truffle/tck/instrumentation/VerifierInstrument.java b/truffle/src/com.oracle.truffle.tck.instrumentation/src/com/oracle/truffle/tck/instrumentation/VerifierInstrument.java
index 41a7ff7a32fd..f4aecf0e0116 100644
--- a/truffle/src/com.oracle.truffle.tck.instrumentation/src/com/oracle/truffle/tck/instrumentation/VerifierInstrument.java
+++ b/truffle/src/com.oracle.truffle.tck.instrumentation/src/com/oracle/truffle/tck/instrumentation/VerifierInstrument.java
@@ -232,7 +232,7 @@ private void verify(final Object result) {
         }
     }
 
-    private static class NodePropertyChecker implements ExecutionEventListener {
+    private static final class NodePropertyChecker implements ExecutionEventListener {
 
         public void onEnter(EventContext context, VirtualFrame frame) {
             Node instrumentedNode = context.getInstrumentedNode();
@@ -254,7 +254,7 @@ public void onReturnExceptional(EventContext context, VirtualFrame frame, Throwa
         }
     }
 
-    private static class RootFrameChecker implements ExecutionEventListener {
+    private static final class RootFrameChecker implements ExecutionEventListener {
 
         @Override
         public void onEnter(EventContext context, VirtualFrame frame) {
@@ -298,7 +298,7 @@ public void onReturnExceptional(EventContext context, VirtualFrame frame, Throwa
         }
     }
 
-    private static class LibraryChecker implements ExecutionEventNodeFactory {
+    private static final class LibraryChecker implements ExecutionEventNodeFactory {
 
         @Override
         public ExecutionEventNode create(EventContext context) {
diff --git a/truffle/src/com.oracle.truffle.tck.tests/src/com/oracle/truffle/tck/tests/InlineExecutionTest.java b/truffle/src/com.oracle.truffle.tck.tests/src/com/oracle/truffle/tck/tests/InlineExecutionTest.java
index d4a2a6eef79b..dd0cbbdc8aff 100644
--- a/truffle/src/com.oracle.truffle.tck.tests/src/com/oracle/truffle/tck/tests/InlineExecutionTest.java
+++ b/truffle/src/com.oracle.truffle.tck.tests/src/com/oracle/truffle/tck/tests/InlineExecutionTest.java
@@ -145,7 +145,7 @@ public void testInline() throws Exception {
         }
     }
 
-    private class TestResultVerifier implements InlineVerifier.ResultVerifier {
+    private final class TestResultVerifier implements InlineVerifier.ResultVerifier {
 
         Exception exception;
 
diff --git a/visualizer/IdealGraphVisualizer/Data/src/main/java/jdk/graal/compiler/graphio/parsing/BinaryReader.java b/visualizer/IdealGraphVisualizer/Data/src/main/java/jdk/graal/compiler/graphio/parsing/BinaryReader.java
index 7b8881c43a1d..983d3c7beed3 100644
--- a/visualizer/IdealGraphVisualizer/Data/src/main/java/jdk/graal/compiler/graphio/parsing/BinaryReader.java
+++ b/visualizer/IdealGraphVisualizer/Data/src/main/java/jdk/graal/compiler/graphio/parsing/BinaryReader.java
@@ -103,7 +103,7 @@ public class BinaryReader implements GraphParser, ModelControl {
 
     private final Builder builder;
 
-    private static class ErrorReporter {
+    private static final class ErrorReporter {
         /**
          * Accumulates names of objects as they are parsed out of stream Used to report context for
          * irrecoverable errors which happen during reading BGV stream.
@@ -184,7 +184,7 @@ public void reportLoadingError(String message, Builder builder) {
         }
     }
 
-    private static class ContextStrings {
+    private static final class ContextStrings {
         private static String propertyGraph(Object s) {
             return String.format("Property %s graph", s);
         }
diff --git a/visualizer/IdealGraphVisualizer/Data/src/main/java/jdk/graal/compiler/graphio/parsing/ModelBuilder.java b/visualizer/IdealGraphVisualizer/Data/src/main/java/jdk/graal/compiler/graphio/parsing/ModelBuilder.java
index c8df87e9c062..d539c0bdcea6 100644
--- a/visualizer/IdealGraphVisualizer/Data/src/main/java/jdk/graal/compiler/graphio/parsing/ModelBuilder.java
+++ b/visualizer/IdealGraphVisualizer/Data/src/main/java/jdk/graal/compiler/graphio/parsing/ModelBuilder.java
@@ -137,7 +137,7 @@ public int hashCode() {
         }
     }
 
-    private static class ErrorMessages {
+    private static final class ErrorMessages {
         public static String edgeStartNodeNotExists(String label, int node) {
             return String.format("Start node for edge %s does not exist: %d", label, node);
         }
diff --git a/visualizer/IdealGraphVisualizer/Data/src/main/java/jdk/graal/compiler/graphio/parsing/model/Properties.java b/visualizer/IdealGraphVisualizer/Data/src/main/java/jdk/graal/compiler/graphio/parsing/model/Properties.java
index b25c90c1a26d..73e5a1ff50ea 100644
--- a/visualizer/IdealGraphVisualizer/Data/src/main/java/jdk/graal/compiler/graphio/parsing/model/Properties.java
+++ b/visualizer/IdealGraphVisualizer/Data/src/main/java/jdk/graal/compiler/graphio/parsing/model/Properties.java
@@ -208,7 +208,7 @@ <TSource extends Iterable<? extends TProp>, TProp> void addFrom(TSource source,
             }
         }
 
-        private class ArrayPropertiesIterator implements Iterator<Property<Object>> {
+        private final class ArrayPropertiesIterator implements Iterator<Property<Object>> {
             int index;
 
             @Override
@@ -575,7 +575,7 @@ public int hashCode() {
         }
     }
 
-    private static class PropertyCache {
+    private static final class PropertyCache {
         static final WeakHashMap</* Shared */ Properties, WeakReference<SharedProperties>> immutableCache = new WeakHashMap<>();
 
         static synchronized SharedProperties intern(Properties properties) {
diff --git a/vm/mx.vm/suite.py b/vm/mx.vm/suite.py
index 4394f6ad43f7..78e5516f526b 100644
--- a/vm/mx.vm/suite.py
+++ b/vm/mx.vm/suite.py
@@ -88,7 +88,7 @@
             "sourceDirs" : ["src"],
             "javaCompliance" : "17+",
             "license" : "GPLv2-CPE",
-            "checkstyleVersion" : "10.7.0",
+            "checkstyleVersion" : "10.21.0",
             "dependencies": [
                 "sdk:LAUNCHER_COMMON",
                 "sdk:POLYGLOT",
diff --git a/wasm/mx.wasm/suite.py b/wasm/mx.wasm/suite.py
index 9fd5ba692afd..9a44cd1cd765 100644
--- a/wasm/mx.wasm/suite.py
+++ b/wasm/mx.wasm/suite.py
@@ -88,7 +88,7 @@
       "requires": [
         "jdk.unsupported", # sun.misc.Unsafe
       ],
-      "checkstyleVersion" : "10.7.0",
+      "checkstyleVersion" : "10.21.0",
       "javaCompliance" : "17+",
       "annotationProcessors" : ["truffle:TRUFFLE_DSL_PROCESSOR"],
       "workingSets" : "WebAssembly",
diff --git a/wasm/src/org.graalvm.wasm.test/src/org/graalvm/wasm/test/AbstractBinarySuite.java b/wasm/src/org.graalvm.wasm.test/src/org/graalvm/wasm/test/AbstractBinarySuite.java
index 7bd5fcbe7fff..9472fea99cc8 100644
--- a/wasm/src/org.graalvm.wasm.test/src/org/graalvm/wasm/test/AbstractBinarySuite.java
+++ b/wasm/src/org.graalvm.wasm.test/src/org/graalvm/wasm/test/AbstractBinarySuite.java
@@ -99,7 +99,7 @@ private static byte getByte(String hexString) {
         return Byte.parseByte(hexString, 16);
     }
 
-    private static class BinaryTypes {
+    private static final class BinaryTypes {
 
         private final List<byte[]> paramEntries = new ArrayList<>();
         private final List<byte[]> resultEntries = new ArrayList<>();
@@ -132,7 +132,7 @@ private byte[] generateTypeSection() {
         }
     }
 
-    private static class BinaryTables {
+    private static final class BinaryTables {
         private final ByteArrayList tables = new ByteArrayList();
 
         private void add(byte initSize, byte maxSize, byte elemType) {
@@ -158,7 +158,7 @@ private byte[] generateTableSection() {
         }
     }
 
-    private static class BinaryMemories {
+    private static final class BinaryMemories {
         private final ByteArrayList memories = new ByteArrayList();
 
         private void add(byte initSize, byte maxSize) {
@@ -182,7 +182,7 @@ private byte[] generateMemorySection() {
         }
     }
 
-    private static class BinaryFunctions {
+    private static final class BinaryFunctions {
         private final ByteArrayList types = new ByteArrayList();
         private final List<byte[]> localEntries = new ArrayList<>();
         private final List<byte[]> codeEntries = new ArrayList<>();
@@ -230,7 +230,7 @@ private byte[] generateCodeSection() {
         }
     }
 
-    private static class BinaryExports {
+    private static final class BinaryExports {
         private final ByteArrayList types = new ByteArrayList();
         private final ByteArrayList indices = new ByteArrayList();
         private final List<byte[]> names = new ArrayList<>();
@@ -260,7 +260,7 @@ private byte[] generateExportSection() {
         }
     }
 
-    private static class BinaryElements {
+    private static final class BinaryElements {
         private final List<byte[]> elementEntries = new ArrayList<>();
 
         private void add(byte[] elements) {
@@ -282,7 +282,7 @@ private byte[] generateElementSection() {
         }
     }
 
-    private static class BinaryDatas {
+    private static final class BinaryDatas {
         private final List<byte[]> dataEntries = new ArrayList<>();
 
         private void add(byte[] data) {
@@ -312,7 +312,7 @@ private byte[] generateDataSection() {
         }
     }
 
-    private static class BinaryGlobals {
+    private static final class BinaryGlobals {
         private final ByteArrayList mutabilities = new ByteArrayList();
         private final ByteArrayList valueTypes = new ByteArrayList();
         private final List<byte[]> expressions = new ArrayList<>();
@@ -340,7 +340,7 @@ private byte[] generateGlobalSection() {
         }
     }
 
-    private static class BinaryCustomSections {
+    private static final class BinaryCustomSections {
         private final List<byte[]> names = new ArrayList<>();
         private final List<byte[]> sections = new ArrayList<>();
 
diff --git a/wasm/src/org.graalvm.wasm.test/src/org/graalvm/wasm/test/suites/wasi/WasiOptionsSuite.java b/wasm/src/org.graalvm.wasm.test/src/org/graalvm/wasm/test/suites/wasi/WasiOptionsSuite.java
index 85bf1c52f31b..273135f170b9 100644
--- a/wasm/src/org.graalvm.wasm.test/src/org/graalvm/wasm/test/suites/wasi/WasiOptionsSuite.java
+++ b/wasm/src/org.graalvm.wasm.test/src/org/graalvm/wasm/test/suites/wasi/WasiOptionsSuite.java
@@ -97,7 +97,7 @@ public static String[][] dirs() {
         };
     }
 
-    private static class TestFileSystem implements FileSystem {
+    private static final class TestFileSystem implements FileSystem {
 
         @Override
         public Path parsePath(URI uri) {
diff --git a/wasm/src/org.graalvm.wasm/src/org/graalvm/wasm/WasmInstantiator.java b/wasm/src/org.graalvm.wasm/src/org/graalvm/wasm/WasmInstantiator.java
index e00cfe146092..acf8addce4d4 100644
--- a/wasm/src/org.graalvm.wasm/src/org/graalvm/wasm/WasmInstantiator.java
+++ b/wasm/src/org.graalvm.wasm/src/org/graalvm/wasm/WasmInstantiator.java
@@ -77,7 +77,7 @@ public class WasmInstantiator {
     private static final int MIN_DEFAULT_STACK_SIZE = 1_000_000;
     private static final int MAX_DEFAULT_ASYNC_STACK_SIZE = 10_000_000;
 
-    private static class ParsingExceptionHandler implements Thread.UncaughtExceptionHandler {
+    private static final class ParsingExceptionHandler implements Thread.UncaughtExceptionHandler {
         private Throwable parsingException = null;
 
         @Override
diff --git a/wasm/src/org.graalvm.wasm/src/org/graalvm/wasm/debugging/encoding/DataEncoding.java b/wasm/src/org.graalvm.wasm/src/org/graalvm/wasm/debugging/encoding/DataEncoding.java
index 6e0f598168a9..fadd478e85af 100644
--- a/wasm/src/org.graalvm.wasm/src/org/graalvm/wasm/debugging/encoding/DataEncoding.java
+++ b/wasm/src/org.graalvm.wasm/src/org/graalvm/wasm/debugging/encoding/DataEncoding.java
@@ -241,7 +241,7 @@ public static int fromForm(int form) {
         };
     }
 
-    private static class Forms {
+    private static final class Forms {
         private static final int ADDR = 0x01;
         private static final int BLOCK2 = 0x03;
         private static final int BLOCK4 = 0x04;