code: public boolean lockIfNotDisposed() {
      boolean result = false;
      if (this.panelLocker != null) {
        this.panelLocker.lock();
        if (this.disposed.get()) {
          this.panelLocker.unlock();
        } else {
          result = true;
        }
      }
      return result;
    }
docs: Try lock the panel if it is not disposed.
  
  @return true if the panel is locked successfully, false if the panel has
  been disposed.