All callback definitions must derive from this interface. Any derived interfaces must define a callback method. You are responsible for deregistering your callback (if necessary) in its Object#finalize method. If native code attempts to call a callback which has been GC'd, you will likely crash the VM. If there is no method to deregister the callback (e.g. atexit in the C library), you must ensure that you always keep a live reference to the callback object.

A callback should generally never throw an exception, since it doesn't necessarily have an encompassing Java environment to catch it.