java单线程。interrupt（）中断多次

Question

我创建了MyTask，它在run()内有3件事要做。我尝试interrupt()保存MyTask实例的线程。不幸的是，一旦中断，它就会结束，控制台上只打印字符串First task

public class MyTask implements Runnable {
    private volatile Thread thread;

    @Override
    public void run() {
        while (!thread.isInterrupted()) {
            System.out.println("First task");
        }
        while (!thread.isInterrupted()) {
            System.out.println("Second task");
        }
        while (!thread.isInterrupted()) {
            System.out.println("Third task");
        }
    }

    public Thread start(){
        thread = new Thread(this);
        thread.start();
        return thread;
    }


    public static void main(String[] args) throws InterruptedException {
        Thread t = new MyTask().start();
        Thread.sleep(1000);
        t.interrupt();
        Thread.sleep(1000);
        t.interrupt();
        Thread.sleep(1000);
        t.interrupt();
    }

}

如果我在run()中添加Thread.sleep(10)，它开始正常工作，并在控制台上打印First task、Second task和最后Third task

问题是：为什么只有当我添加sleep()时Thread.interrupts()才能正常工作

public class MyTask implements Runnable {
    private volatile Thread thread;

    @Override
    public void run() {
        while (!thread.isInterrupted()) {
            System.out.println("First task");
        }
        try {
            Thread.sleep(10);
        } catch (Exception e) {
        }
        while (!thread.isInterrupted()) {
            System.out.println("Second task");
        }
        try {
            Thread.sleep(10);
        } catch (Exception e) {
        }
        while (!thread.isInterrupted()) {
            System.out.println("Third task");
        }
    }

    public Thread start(){
        thread = new Thread(this);
        thread.start();
        return thread;
    }


    public static void main(String[] args) throws InterruptedException {
        Thread t = new MyTask().start();
        Thread.sleep(1000);
        t.interrupt();
        Thread.sleep(1000);
        t.interrupt();
        Thread.sleep(1000);
        t.interrupt();
    }

}

Answer 1

请看一下Thread.sleep(long)上的Javadoc

Throws: InterruptedException - if any thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.

因此，添加sleep以及捕获（并输入）任何异常将导致观察到的行为

例如：

没有sleep()：

• 线程以interrupted = false开始，因此第一个循环运行
• 线程被中断，即现在interrupted = true
• 第一个循环检查interrupted并且没有运行（再次）
• 第二个循环检查interrupted并且根本不运行
• 第三个循环检查interrupted并且根本不运行
• 完成

用sleep()

1. 线程以interrupted = false开头

2. 循环1：

   • 自interrupted = false起检查条件并执行正文时
   • 线程被中断，即现在interrupted = true
   • 虽然条件已检查，但这次interrupted = true因此循环结束
   • ^调用{}，由于线程被中断，因此抛出异常并再次interrupted = false
   • 捕获（并忽略）异常，因此正常继续执行

3. 对循环2和3重复步骤2

4. 完成

Answer 2

引自Interrupts：

When a thread checks for an interrupt by invoking the static method Thread.interrupted, interrupt status is cleared. The non-static isInterrupted method, which is used by one thread to query the interrupt status of another, does not change the interrupt status flag.

意思：将代码从thread.isInterrupted()更改为Thread.interrupted()，然后重试

循环之间的sleep()也将通过立即抛出InterruptedException清除该标志（因为当前线程已被中断）