if (path.length() == 0) return true;
  public boolean changeWorkingDirectory(String path)    throws IOException  {    String cmd = CWD + ' ' + path;    send(cmd);    FTPResponse response = getResponse();    switch (response.getCode())      {      case 250:        return true;      case 550:        return false;      default:        throw new FTPException(response);      }  }