code: public boolean isSet(_Fields field) {
      if (field == null) {
        throw new IllegalArgumentException();
      }
  
      switch (field) {
      case PATH:
        return isSetPath();
      case LENGTH:
        return isSetLength();
      case ISDIR:
        return isSetIsdir();
      case MODIFICATION_TIME:
        return isSetModification_time();
      case ACCESS_TIME:
        return isSetAccess_time();
      }
      throw new IllegalStateException();
    }
docs: Returns true if field corresponding to fieldID is set (has been assigned a value) and false otherwise