Don't Use Finalizers

It is almost certainly wrong to use finalizers.

Finalizers…

• are not promptly executed,
• can arbitrarily delay reclamation (and result in OutOfMemoryError),
• are not guaranteed to be executed,
• ignore exceptions during finalization (and leave corrupted object not reclaimed),
• add severe performance penalty.

The bottom line is, don’t use finalizers; use an explicit close() method instead. You should maintain a isClosed boolean state (and usually throw IllegalStateException on multiple close() calls).

The probably only legitimate use of finalizer is when you have native peers (JVM does not know how to release these native resources). However, if the native resources must be released promptly, you should provide an explicit close() method.

Note: Don’t forget to call superclass’ finalizer unconditionally:

@Override
protected void finalize() throws Throwable {
  try {
    ... // Finalize subclass state.
  } finally {
    super.finalize();
  }
}

…or use finalizer guardian.