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?

Answer 1

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

Answer 2

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/