@Override protected void deleteLast(final byte[] key){
  final Lock lock=writeLock();
  lock.lock();
  try {
    super.deleteLast(key);
  }
  finally {
    unlock(lock);
  }
}

@ Override protected void deleteLast ( final byte [ ] key ) { final Lock lock = writeLock ( ) ; lock . lock ( ) ; try { super . deleteLast ( key ) ; } finally { unlock ( lock ) ; } }
extended to acquire the exclusive write lock .
