#fixed code
                              @Override
  public void handleDataChange(String dataPath, Object data) {
    if (_zkClientForRoutingDataListener == null || _zkClientForRoutingDataListener.isClosed()) {
      return;
    }
    resetZkResources();
  }
#vulnerable code 
                              @Override
  public void handleDataChange(String dataPath, Object data) {
    if (_zkClientForListener == null || _zkClientForListener.isClosed()) {
      return;
    }
    resetZkResources();
  } 
                            #location 3 
                            #vulnerability type THREAD_SAFETY_VIOLATION