code: @Override
    public void stop() {
      if (!stopped.compareAndSet(false, true)) return;
  
      sweep();
  
      int retries = 0;
      while (count() > 1 && ++retries < 10) {
        try { Thread.sleep(10L); } catch (Exception e) {}
      }
  
      scheduler.close();
    }
docs: Initiates the process of stopping this {@code Stage}.