code: public boolean reset() {
          try (Locker.Lock lock = _locker.lock()) {
              switch (_state) {
                  case IDLE:
                      return true;
  
                  case SUCCEEDED:
                  case FAILED:
                      _iterate = false;
                      _state = State.IDLE;
                      return true;
  
                  default:
                      return false;
              }
          }
      }
docs: Resets this callback.
  <p>
  A callback can only be reset to IDLE from the
  SUCCEEDED or FAILED states or if it is already IDLE.
  </p>
  
  @return true if the reset was successful