定时执行的线程池

private static void scheduled(){
  //创建一个定时执行的线程池
  ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(3);
  scheduledExecutorService.schedule(() -> {
      System.out.println("延迟3秒");
  }, 3 , TimeUnit.SECONDS);

  scheduledExecutorService.scheduleAtFixedRate(() -> {
      System.out.println("延迟 1 秒后每三秒执行一次");
  }, 1, 3, TimeUnit.SECONDS);

  //scheduledExecutorService.shutdown();
}