if (next != null) { next.push (newEventQueue); return; }
  public synchronized void push(EventQueue newEventQueue)  {    if (newEventQueue == null)      throw new NullPointerException ();    int i = next_out;    while (i != next_in)      {        newEventQueue.postEvent(queue[i]);        next_out = i;        if (++i == queue.length)          i = 0;      }    next = newEventQueue;    newEventQueue.prev = this;      }