UUID
Java 1.4 (and before)
Java Uuid Generator (JUG)
Sample
UUID uuid = UUIDGenerator.getInstance().generateRandomBasedUUID();
Maven 2
<dependency>
<groupId>org.safehaus.jug</groupId>
<artifactId>jug</artifactId>
<version>2.0.0</version>
<classifier>asl</classifier>
</dependency>