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Groups > comp.lang.java.programmer > #7091

Singleton Pattern

From "vbhavsar@gmail.com" <vbhavsar@gmail.com>
Newsgroups comp.lang.java.programmer
Subject Singleton Pattern
Date 2011-08-13 13:56 -0700
Organization http://groups.google.com
Message-ID <3be6e6cf-fa32-4503-9457-b0a1caef8f29@w11g2000vbp.googlegroups.com> (permalink)

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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?

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Thread

Singleton Pattern "vbhavsar@gmail.com" <vbhavsar@gmail.com> - 2011-08-13 13:56 -0700
  Re: Singleton Pattern markspace <-@.> - 2011-08-13 14:41 -0700
  Re: Singleton Pattern Patricia Shanahan <pats@acm.org> - 2011-08-13 14:48 -0700
  Re: Singleton Pattern Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-08-13 16:43 -0700
    Re: Singleton Pattern Ian <m4r35n357@gmail.com> - 2011-08-15 15:00 +0100
      Re: Singleton Pattern Lew <lewbloch@gmail.com> - 2011-08-15 07:56 -0700
        Re: Singleton Pattern Patricia Shanahan <pats@acm.org> - 2011-08-15 22:07 -0700
          Re: Singleton Pattern Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-08-16 00:09 -0700
            Re: Singleton Pattern Patricia Shanahan <pats@acm.org> - 2011-08-16 06:15 -0700
              Re: Singleton Pattern Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-08-16 06:57 -0700
                Re: Singleton Pattern Patricia Shanahan <pats@acm.org> - 2011-08-16 09:25 -0700
                Re: Singleton Pattern Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-08-16 18:10 -0700
  Re: Singleton Pattern Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-13 20:56 -0400
    Re: Singleton Pattern Lew <lewbloch@gmail.com> - 2011-08-13 21:12 -0700
  Re: Singleton Pattern Rajeev <rajeev.nospam@gmail.com> - 2011-08-14 06:37 -0700

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