Performs cleanup associated with termination of this worker
thread. If you override this method, you must invoke
{@code super.onTermination} at the end of the overridden method.
@param exception the exception causing this thread to abort due
to an unrecoverable error, or {@code null} if completed normally
Performs cleanup associated with termination of this worker thread. If you override this method, you must invoke {@code super.onTermination} at the end of the overridden method.
@param exception the exception causing this thread to abort due to an unrecoverable error, or {@code null} if completed normally