code: public synchronized boolean runOneTask() {
      ScheduledRunnable postedRunnable = runnables.poll();
      if (postedRunnable != null) {
        if (postedRunnable.scheduledTime > currentTime) {
          currentTime = postedRunnable.scheduledTime;
        }
        postedRunnable.run();
        return true;
      }
      return false;
    }
docs: Run the next runnable in the queue.
  
  @return  True if a runnable was executed.