控制线程顺序的两种简易方法

1、利用线程的join方法，暂停正在运行的线程，执行调用join的线程。强制参与进来。

 private static void testMethod1(){
        Thread threadA = new Thread(() -> System.out.println("A"));
        Thread threadB = new Thread(() -> System.out.println("B"));
        Thread threadC = new Thread(() -> System.out.println("C"));
        try {
            threadA.start();
            threadA.join();
            threadB.start();
            threadB.join();
            threadC.start();
            threadC.join();
        }catch (Exception e){
            e.printStackTrace();
        }
    }

 

2、利用线程池的特性，这里是利用了核心线程数和最大线程数为1以及等待队列有序的特性，线程池中只存在一个线程，后加进来的两个线程都在进入等待队列中，按顺序进入。当线程A的任务执行完成，B任务进入，最后C任务进入。

 private static void testMethod2(){
        Thread threadA = new Thread(() -> System.out.println("A"));
        Thread threadB = new Thread(() -> System.out.println("B"));
        Thread threadC = new Thread(() -> System.out.println("C"));
        ThreadPoolExecutor threadExecutor = new ThreadPoolExecutor(1,1,1000, TimeUnit.SECONDS,new ArrayBlockingQueue<>(10),new ThreadPoolExecutor.AbortPolicy());
        threadExecutor.execute(threadA);
        threadExecutor.execute(threadB);
        threadExecutor.execute(threadC);
        threadExecutor.shutdown();
    }

 

3、两者的实现效果：