Can garbage Collector deallocate singleton instance? (and why or how to avoid it)

Question

In Android I have singleton class but I am not sure if the garbage Collector can deallocate it.

If garbage Collector will deallocate my singleton class how can avoid it from deallocation?

There is convention of using WeakReference, try to use that. — hackp0int, Mar 02 '13 at 16:13

score 3 · Answer 1 · edited May 23 '17 at 11:52

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Garbage collection collects objects that nothing is pointed to, unless a reference is static. Are static fields open for garbage collection?

edited May 23 '17 at 11:52

Community

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answered Mar 02 '13 at 16:10

Shellum

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There is no such thing, in Java, as a "static object". – G. Blake Meike Mar 02 '13 at 16:39
An object's structure cannot be declared static, but you can have a static reference/instance of it. Answer edited to say reference. – Shellum Mar 02 '13 at 19:37
Yeah! I think, though, that you could just leave out the whole thing about static references. Your answer is complete and correct, at the comma! – G. Blake Meike Mar 02 '13 at 19:57

score 2 · Answer 2 · answered Mar 02 '13 at 16:08

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The only reason gc will dealocate your instance is if the entire app is destroyed...

answered Mar 02 '13 at 16:08

Chen Kinnrot

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This is patently false: Consider: `static { new Object(); }` That is a singleton and it is garbage collected instantly. – G. Blake Meike Mar 02 '13 at 16:40

G. Blake Meike · Answer 3 · 2013-03-02T19:57:38.993

There are lots of ways to implement a Singleton. One of the best is:

public static enum My { SINGLETON; }

Whether or not something is a singleton has no bearing on whether it is GCed or not. An object will be GCed if there are no Strong references to it. Look it up (http://weblogs.java.net/blog/2006/05/04/understanding-weak-references).

There is one more issue that is of interest. In Android, your application does not control it's lifecycle. It is possible that a process will be terminated and re-created in ways you do not expect. If that happens, static final variables will be re-initialized. There's more on that here:

http://portabledroid.wordpress.com/2012/05/04/singletons-in-android/

Can garbage Collector deallocate singleton instance? (and why or how to avoid it)

3 Answers3