Example

UUID is the fastest and easiest way to generate unique ID in Java.

import java.util.UUID;  
public class UniqueIDTest {  
 public static void main(String[] args) {  
  UUID uniqueKey = UUID.randomUUID();   
  System.out.println (uniqueKey);  
}  
}

Result

0a6a3de7-b974-42d0-af9e-9c23473b09b9
You might also like this tutorials :
Struts 2.x Tutorials
Spring Tutorials
JDBC Tutorials
JAX-RS Tutorials
Java MongoDB Tutorials