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From: "vbhavsar@gmail.com" <vbhavsar@gmail.com>
Newsgroups: comp.lang.java.programmer
Subject: Singleton Pattern
Date: Sat, 13 Aug 2011 13:56:34 -0700 (PDT)
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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?