Re: Singletons?

"Oliver Wong" <>
Tue, 13 Jun 2006 20:05:58 GMT
"Ian Shef" <invalid@avoiding.spam> wrote in message

"Oliver Wong" <> wrote in


FWIW, here's how I
usually implement Singleton in Java:

public class Variant1 {
  private static Variant1 soleInstance = null;

  private Variant1() {
    /*You should declare all your constructors private, to avoid
instantiation. If you don't have any constructors, then create an empty,
zero argument, private constructor like this one.*/

  public static Variant1 getSoleInstance() {
    if (soleInstance == null) {
      soleInstance = new Variant1();
    return soleInstance;

Are you operating in a single thread environment only?

    Yes. [*]

 Where is your
synchronization? Two threads can call getSoleInstance concurrently, and
end up with different instances of Variant1. See

    Perhaps I should make it a habit to consider concurrency issues more

    - Oliver

[*] Discounting the garbage collector thread, and other threads that
automagically appear but which don't make calls into my code.

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