New factory method to create TimeBasedEpochRandomGenerator (#99)

Author: worldtiki

release-notes/CREDITS

@@ -143,3 +143,8 @@ Pavel Raev (magdel@github)
 Maia Everett (Maia-Everett@github)
   * Contributed #85: Fix `LazyRandom` for native code generation tools
    [5.0.0]
+
+Daniel Albuquerque (worldtiki@github)
+  * Contributed #99: New factory method to create TimeBasedEpochRandomGenerator
+   [5.1.0]
+

release-notes/VERSION

@@ -4,6 +4,11 @@ Project: java-uuid-generator
 Releases
 ============================================================================
 
+5.1.0 (not yet released)
+
+#99: New factory method to create TimeBasedEpochRandomGenerator
+ (contributed by Daniel A)
+
 5.0.0 (23-Feb-2024)
 
 #53: Increase JDK baseline to JDK 8

src/main/java/com/fasterxml/uuid/Generators.java

@@ -126,6 +126,11 @@ public static NameBasedGenerator nameBasedGenerator(UUID namespace, MessageDiges
     /**
      * Factory method for constructing UUID generator that generates UUID using
      * version 7 (Unix Epoch time+random based).
+     *<p>
+     * NOTE: calls within same millisecond produce very similar values; this may be
+     * unsafe in some environments.
+     *<p>
+     * No additional external synchronization is used.
      */
     public static TimeBasedEpochGenerator timeBasedEpochGenerator()
     {
@@ -166,6 +171,24 @@ public static TimeBasedEpochGenerator timeBasedEpochGenerator(Random random,
         return new TimeBasedEpochGenerator(random, clock);
     }
 
+    // // Epoch Time+random generation
+
+    /**
+     * Factory method for constructing UUID generator that generates UUID using
+     * version 7 (Unix Epoch time+random based).
+     *<p>
+     * Calls within same millisecond use additional per-call randomness to try to create
+     * more distinct values, compared to {@link #timeBasedEpochGenerator(Random)}
+     *<p>
+     * No additional external synchronization is used.
+     *
+     * @since 5.1
+     */
+    public static TimeBasedEpochRandomGenerator timeBasedEpochRandomGenerator()
+    {
+        return timeBasedEpochRandomGenerator(null);
+    }
+
     /**
      * Factory method for constructing UUID generator that generates UUID using
      * version 7 (Unix Epoch time+random based), using specified {@link Random}

src/test/java/com/fasterxml/uuid/impl/UUIDUtilTest.java

@@ -61,6 +61,16 @@ public void testExtractTimestampUUIDEpochBased() {
         }
     }
 
+    public void testExtractTimestampUUIDEpochRandomBased() {
+        TimeBasedEpochRandomGenerator generator = Generators.timeBasedEpochRandomGenerator();
+        final Random rnd = new Random(3);
+        for (int i = 0; i < TEST_REPS; i++) {
+            long rawTimestamp = rnd.nextLong() >>> 16;
+            UUID uuid = generator.construct(rawTimestamp);
+            assertEquals(rawTimestamp, UUIDUtil.extractTimestamp(uuid));
+        }
+    }
+
     public void testExtractTimestampUUIDOnOtherValues() {
         assertEquals(0L, UUIDUtil.extractTimestamp(null));
         assertEquals(0L, UUIDUtil.extractTimestamp(UUID.fromString("00000000-0000-0000-0000-000000000000")));