让主线程等待其他线程完成

Question

我有以下Switch 类，基本上是toggles isOn

我想主要是制作thread1 和thread2，启动它们， 然后睡 5 秒，然后interrupt 他们，我认为我这样做是正确的

除了主线程应该等待两个线程完成，这就是我添加的地方

thread1.join()
thread2.join()

但这导致线程永远运行并且没有抛出异常，我应该怎么做？还是 main 已经在等待他们完成？

public class Switch implements Runnable {
    private static boolean isOn;
    private String name;
    private static final Object lockedObject = new Object();

    public Switch(String name) {
        this.name = name;
    }

    public void toggle() {
        System.out.println(name + ": " + isOn);
        synchronized (lockedObject) {
            isOn = !isOn;
        }
    }

    @Override
    public void run() {
        while (true) {
            if (Thread.currentThread().isInterrupted()) {
                break;
            }
            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {
                e.printStackTrace();
                break;
            }
            synchronized (lockedObject) {
                toggle();
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
        Switch switch1 = new Switch("switch1");
        Switch switch2 = new Switch("switch2");
        Thread thread1 = new Thread(switch1);
        Thread thread2 = new Thread(switch2);
        thread1.start();
        thread2.start();
//        thread1.join();
//        thread2.join();
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        thread1.interrupt();
        thread2.interrupt();
    }
}

Answer 1

您需要在catch 块中加入以下行：

Thread.currentThread().interrupt();

另外，您不需要以下几行：

if (Thread.currentThread().isInterrupted()) {
    break;
}

演示：

public class Switch implements Runnable {
    private static boolean isOn;
    private String name;
    private static final Object lockedObject = new Object();

    public Switch(String name) {
        this.name = name;
    }

    public void toggle() {
        System.out.println(name + ": " + isOn);
        synchronized (lockedObject) {
            isOn = !isOn;
        }
    }

    @Override
    public void run() {
        while (true) {
            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();// Add this line
                break;
            }
            synchronized (lockedObject) {
                toggle();
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
        Switch switch1 = new Switch("switch1");
        Switch switch2 = new Switch("switch2");
        Thread thread1 = new Thread(switch1);
        Thread thread2 = new Thread(switch2);
        thread1.start();
        thread2.start();
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        thread1.interrupt();
        thread2.interrupt();
    }
}