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?

Consensual

There is convention of using WeakReference, try to use that. – Leoraleos

Answer 1

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

Outleap

There is no such thing, in Java, as a "static object". – Lamasery

An object's structure cannot be declared static, but you can have a static reference/instance of it. Answer edited to say reference. – Outleap

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! – Lamasery

Answer 2

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

Warfore

This is patently false: Consider: static { new Object(); } That is a singleton and it is garbage collected instantly. – Lamasery

Answer 3

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/

Lamasery