Eagerly created singleton design

[surya.raaj prakash]

Hi Friends,

 public class Singleton
                 {
               private static final Singleton SINGLE = new Singleton();

               public void onlyOneInstance() {.....}

                  }

Has anybody else here read the above singleton design and if so, what are your thoughts Regarding this design in mulithreaded environment?will multiple different objects create or single object create by multiple threads?

[Campbell Ritchie]

Please search this forum; there are questions about singletons several times a month. Also, I think this is too complicated for "beginning", so I shall move the thread.

[Mike Simmons]

Surya - normally you'd also provide a private constructor. Otherwise, it's easy for anyone to create their own instance.

You'd also normally want to provide some public way to obtain a reference to the SINGLE reference. Right now it's private, and no other code references it. Maybe you intend to use SINGLE inside onlyOneInstance(), but that method returns a void, so it can't make the reference available to the outside world. To be honest, I have no idea what onlyOneInstance() might do, as shown.

Aside from those issues...

surya.raaj prakash wrote:Has anybody else here read the above singleton design and if so, what are your thoughts Regarding this design in mulithreaded environment?

Yes, this is simpler than a lazy-loaded singleton, so people don't discuss it as much. But a properly-coded eagerly-loaded singleton can be quite thread-safe, yes.

surya.raaj prakash wrote:will multiple different objects create or single object create by multiple threads?

Um, if you make a private constructor (the only constructor), and if you provide a public method that returns the instance... then there should be only one instance, shared by all threads.

I'm going to skip all the usual anti-singleton rhetoric, as I expect someone will be along shortly to point you towards all that. I just wanted to address the specifics of your post.