@Override
  protected boolean removeMapping(Object o) {
    Lock l = writeLock();
    l.lock();
    try {
      return super.removeMapping(o);
    } finally {
      l.unlock();
    }
  }
@ Override protected boolean removeMapping ( Object o ) { Lock l = writeLock ( ) ; l . lock ( ) ; try { return super . removeMapping ( o ) ; } finally { l . unlock ( ) ; } }
/*
remove used by EntrySet