A class that represents an immutable universally unique identifier (UUID). A UUID represents a 128-bit value. There exist different variants of these global identifiers. 

import java.util.UUID;  
public class UUIDExample   
{  
public static void main(String[] args)   
{  
UUID uuid=UUID.randomUUID(); //Generates random UUID  
System.out.println(uuid);  
}  
}  
Output

c6a8669e-ee95-4c42-9ef6-4a9b61380164