Avoid Unintentional Object Retention

Unintentional object retention (or informally called memory leaking) can be fixed by nulling out references once they become obsolete.

• But don’t overcompensate by nulling out every object references! You usually need to null out references when you manage memory yourself (say, implementing a stack).
• The second common source of memory leaking is cache.
  • Use weak references or WeakHashMap.
• The third common source (and harder to be noticed) is listeners or callbacks.
  • If a user forgets to deregister his callbacks, these callbacks are leaked.
  • Use weak references for callbacks.