How do I generate UUID / GUID?

UUID / GUID (Universally / Globally Unique IDentifier) are frequently use in programming. Some of its usage are for creating random file names, session id in web application, transaction id and for record's primary keys in database replacing the sequence or auto generated number.

import java.util.UUID;
public class RandomStringUUID {
    public static void main(String[] args) {
        //
        // Creating a random UUID (Universally unique identifier).
        //
        UUID uuid = UUID.randomUUID();
        String randomUUIDString = uuid.toString();
        System.out.println("Random UUID String = " + randomUUIDString);
        System.out.println("UUID version       = " + uuid.version());
        System.out.println("UUID variant       = " + uuid.variant());
    }
}