Annotate ClassValue. (#119)

Co-authored-by: Werner Dietl <[email protected]>

Author: cpovirk

src/java.base/share/classes/java/lang/ClassValue.java

@@ -31,6 +31,9 @@
 
 import jdk.internal.misc.Unsafe;
 
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
 import static java.lang.ClassValue.ClassValueMap.probeHomeLocation;
 import static java.lang.ClassValue.ClassValueMap.probeBackupLocations;
 
@@ -44,7 +47,8 @@
  * @author John Rose, JSR 292 EG
  * @since 1.7
  */
-public abstract class ClassValue<T> {
+@NullMarked
+public abstract class ClassValue<T extends @Nullable Object> {
     /**
      * Sole constructor.  (For invocation by subclass constructors, typically
      * implicit.)