#vulnerable code 
                              @Override
  public void close() {
    if (_zkclient != null) {
      _zkclient.close();
    }
  } 
                            #location 4 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                              @Override
  public void close() {
    if (_zkClient != null) {
      _zkClient.close();
    }
  }