Added UuidUtils add method. (#43)

* Added UuidUtils.add method.

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.12.1] - 2023-10-29
+
+### Added
+
+* UuidUtils.add method.
+
 ## [1.12.0] - 2023-10-03
 
 ### Changed

gradle.properties

@@ -1 +1 @@
-version=1.12.0
+version=1.12.1

tw-base-utils/src/main/java/com/transferwise/common/baseutils/UuidUtils.java

@@ -92,6 +92,15 @@ public static byte[] toBytes(UUID uuid) {
     return bytes;
   }
 
+  public static UUID add(UUID uuid, long constant) {
+    if (uuid == null) {
+      throw new NullPointerException("Can not add anything to null.");
+    }
+
+    // Can overflow, but this is fine.
+    return new UUID(uuid.getMostSignificantBits(), uuid.getLeastSignificantBits() + constant);
+  }
+
   protected static long applyVersionBits(final long msb, int versionBits) {
     return (msb & 0xffffffffffff0fffL) | versionBits;
   }

tw-base-utils/src/test/java/com/transferwise/common/baseutils/UuidUtilsTest.java

@@ -2,7 +2,9 @@
 
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import com.google.common.collect.Ordering;
@@ -11,6 +13,7 @@
 import java.util.Arrays;
 import java.util.Set;
 import java.util.UUID;
+import java.util.concurrent.ThreadLocalRandom;
 import org.apache.commons.lang3.RandomUtils;
 import org.junit.jupiter.api.Test;
 
@@ -45,6 +48,45 @@ void defaultPrefixCombUuidIsGrowingOverTime() {
     assertEquals(n, Set.of(uuids).size());
   }
 
+  @Test
+  void constantCanBeAddedToUuid() {
+    var uuid = UuidUtils.generatePrefixCombUuid();
+    var uuidWithConstant = UuidUtils.add(uuid, 11111);
+
+    assertNotEquals(uuidWithConstant, uuid);
+
+    assertThrows(NullPointerException.class, () -> UuidUtils.add(null, 0));
+  }
+
+  @Test
+  void addingConstantDoesNotChangeOrdering() {
+    TestClock clock = TestClock.createAndRegister();
+
+    int n = 100;
+
+    UUID[] uuids = new UUID[n];
+    for (int i = 0; i < n; i++) {
+      uuids[i] = UuidUtils.add(UuidUtils.generatePrefixCombUuid(), ThreadLocalRandom.current().nextInt());
+      clock.tick(Duration.ofMillis(2));
+    }
+
+    long previousTime = -1;
+    for (int i = 0; i < n; i++) {
+      long time = uuids[i].getMostSignificantBits() >>> (64 - 38);
+
+      if (previousTime != -1) {
+        assertTrue(previousTime < time);
+      }
+      previousTime = time;
+
+      System.out.println(uuids[i]);
+      assertEquals(4, uuids[i].version());
+    }
+
+    assertTrue(Ordering.natural().isOrdered(Arrays.asList(uuids)));
+    assertEquals(n, Set.of(uuids).size());
+  }
+
   @Test
   void convertingFromUuidAndBackToBytesEndWithTheSameResult() {
     UUID expected = UUID.randomUUID();