Java实现保证多个线程执行完毕再往下执行操作

news2024/11/15 5:13:23

要实现该需求可借助线程池的awaitTermination和isTerminated方法来实现，也可使用CountDownLatch计数器来实现。

1.使用awaitTermination方法阻塞主线程, 直至线程池关闭

    public static void main(String[] args) throws InterruptedException {


        ExecutorService threadPool= Executors.newFixedThreadPool(10);
        threadPool.submit(() -> {
            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("休息5秒-----------------------------");
       
        });
        threadPool.submit(() -> {
            try {
                Thread.sleep(15000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("休息15秒-----------------------------");
       
        });
        threadPool.submit(() -> {
            try {
                Thread.sleep(10000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("休息10秒-----------------------------");
  
        });


        threadPool.shutdown();

        threadPool.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
       System.out.println("执行结束！");

    }

运行结果

2.使用isTerminated方法，当调用shutdown()后，线程提交任务完成时变为true

 public static void main(String[] args)  {


        ExecutorService threadPool= Executors.newFixedThreadPool(10);
        threadPool.submit(() -> {
            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("休息5秒-----------------------------");

        });
        threadPool.submit(() -> {
            try {
                Thread.sleep(15000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("休息15秒-----------------------------");

        });
        threadPool.submit(() -> {
            try {
                Thread.sleep(10000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("休息10秒-----------------------------");

        });
        
        threadPool.shutdown();
        while (!threadPool.isTerminated()){
            if (threadPool.isTerminated())   break;

        }
       System.out.println("执行结束！");

    }

运行结果

3.使用CountDownLatch该方法不依赖于线程池，但是需知道有多少个线程，通过countDown方法减少对应线程计数实现。

 public static void main(String[] args) throws InterruptedException {
        CountDownLatch count = new CountDownLatch(3);
        ExecutorService threadPool= Executors.newFixedThreadPool(10);
        threadPool.submit(() -> {
            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("休息5秒-----------------------------");
            count.countDown();
        });
        threadPool.submit(() -> {
            try {
                Thread.sleep(15000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("休息15秒-----------------------------");
            count.countDown();
        });
        threadPool.submit(() -> {
            try {
                Thread.sleep(10000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("休息10秒-----------------------------");
            count.countDown();
        });

        threadPool.shutdown();
        count.await();
       System.out.println("执行结束！");

    }

运行结果