@Test
public void billiardTest() throws Exception {
   // 创建点外卖线程:
   CompletableFuture<Boolean> takeaway = CompletableFuture.supplyAsync(() -> {
       System.out.println("开始点外卖");
       try {
           System.out.println("外卖 => 下单");
           Thread.sleep(1000);
           System.out.println("外卖 => 店家接单开始做饭");
           Thread.sleep(10000);
           System.out.println("外卖 => 做饭完成骑手接单");
           Random random = new Random();
           int time = random.nextInt(5);
           Thread.sleep(time * 1000);
           System.out.println("外卖 => 外卖已送达");
       } catch (InterruptedException e) {
           e.printStackTrace();
       }
       return true;
   });
   //创建打球线程
   CompletableFuture<Boolean> billiard = takeaway.supplyAsync(() -> {
       System.out.println("开始打桌球");
       //直接用线程的返回值，不用中间变量，防止变量被篡改
       while (!takeaway.getNow(false)) {
           try {
               System.out.println("打球 => 摆球");
               Thread.sleep(1000);
               System.out.println("打球 => 打球");
               Thread.sleep(5000);
               System.out.println("打球 => 打球结束确定输赢");
           } catch (InterruptedException e) {
               e.printStackTrace();
           }
       }
       System.out.println("外卖已到，不再打球");
       return true;
   });
   //打球的结束，依赖外卖，所以这边只需要看打球是否结束来确定是不是开始吃饭
   billiard.thenAccept((param) -> {
       System.out.println("开始吃饭");
   });
   //主线程可以做其它事
   while (true) {
       System.out.println("主线程可以做其它事：" + DateUtil.now());
       Thread.sleep(1000);
   }
}