Re: Singleton Pattern

People have been coming up with creative solutions to lazily implement
the singleton pattern in a thread-safe way. We have seen things like
double-checked locking and creating instance via a single-elemnt enum
type.

I have thought of yet another way to implement this in a lazy and
thread-safe way. I haven't seen this proposed anywhere and it seems to
work unless I am missing something. Here it goes:

public class Singleton {

    private static Singleton _instance;
    private Singleton(){}

    private synchronized static void createInstance(){
        _instance = new Singleton();
    }

    public static Singleton getInstance(){
        if (_instance == null){
            createInstance();
        }
        return _instance;
    }
}

The synchronized createInstance() method would eliminate the need to
do double-checked locking and the synchronization would happen only
when multiple threads call getInstance() before _instance has been
instantiated.

Anyone see any issues with this?