线程中断interrupt()、interrupted()和isInterrupted()方法详解线程中断interru

interrupt()

thread.interrupt()，该方法用于中断Thread线程，此线程并非当前线程，而是调用interrupt()方法的实例所代表的线程，并不是强制关闭线程，而是将中断标记位设置为true，线程的中断需要在线程内部协作关闭

interrupted()

interrupted()为静态方法，判断当前线程的中断状态，并会将中断标记位设置为false，在第二次调用时中断状态会返回false

isInterrupted()

thread.isInterrupted()，用于判断thread的中断状态，不清除中断状态

public class MyThread extends Thread {

    public MyThread(String name) {
        super(name);
    }

    @Override
    public void run() {
        for (int i = 0; i < 100; ++i) {
            System.out.println("i : " + i);
        }
    }
}

public class InterruptTest {

    public static void main(String[] args) {
        MyThread myThread = new MyThread("my-thread");
        myThread.start();

        // 中断myThread线程，myThread线程的中断标记位设置为true
        myThread.interrupt();

        System.out.println("myThread.isInterrupted() : " + myThread.isInterrupted());
        System.out.println("myThread.isInterrupted() : " + myThread.isInterrupted());
        System.out.println("myThread.isAlive() : " + myThread.isAlive());

        System.out.println("main.isInterrupted() : " + Thread.currentThread().isInterrupted());
    }
}

输出结果： myThread.isInterrupted() : true myThread.isInterrupted() : true myThread.isAlive() : true main.isInterrupted() : false

结论

myThread.isInterrupted()结果为true，main.isInterrupted()结果为false，则证明myThread.interrupt()方法是对myThread实例所对应线程设进行的中断操作
myThread.isInterrupted()执行了两次均返回true，则说明isInterrupted()方法仅仅返回myThread线程的中断状态，不清除中断状态
myThread.isAlive()结果为true，则证明isInterrupted()并不会直接中断线程，而仅仅是将中断标记位设置为true

public class InterruptedTest {

    public static void main(String[] args) {

        MyThread myThread = new MyThread("my-thread");

        myThread.start();

        myThread.interrupt();

        Thread.currentThread().interrupt();

        System.out.println("执行前-myThread.isInterrupted() : " + myThread.isInterrupted());

        System.out.println("执行前-myThread.isInterrupted() : " + myThread.isInterrupted());

        System.out.println("执行前-main.isInterrupted() : " + Thread.currentThread().isInterrupted());

        System.out.println("执行前-main.isInterrupted() : " + Thread.currentThread().isInterrupted());

        System.out.println("main interrupted() : " + Thread.interrupted());

        System.out.println("main interrupted() : " + Thread.interrupted());

        System.out.println("执行后-myThread.isInterrupted() : " + myThread.isInterrupted());

        System.out.println("执行后-myThread.isInterrupted() : " + myThread.isInterrupted());

        System.out.println("执行后-main.isInterrupted() : " + Thread.currentThread().isInterrupted());

        System.out.println("执行后-main.isInterrupted() : " + Thread.currentThread().isInterrupted());
    }
}

输出结果：执行前-myThread.isInterrupted() : true 执行前-myThread.isInterrupted() : true 执行前-main.isInterrupted() : true 执行前-main.isInterrupted() : true main interrupted() : true main interrupted() : false 执行后-myThread.isInterrupted() : true 执行后-myThread.isInterrupted() : true 执行后-main.isInterrupted() : false 执行后-main.isInterrupted() : false

结论

main.isInterrupted()执行前后结果不一致，myThread.isInterrupted()执行前后结果一直，则证明interrupted()方法作用在当前线程
Thread.interrupted()第一次执行为true，第二次执行为false，则证明该方法会清除中断状态

由于interrupt()方法不是真正的去中断线程，可以在run()方法内判断中断状态，当为true时则去执行停止线程的操作

public class MyThread extends Thread {

    public MyThread(String name) {
        super(name);
    }

    @Override
    public void run() {
        for (int i = 0; i < 100; ++i) {

            System.out.println("i : " + i);

            boolean interrupted = Thread.currentThread().isInterrupted();
            if (interrupted) {
                // 判断为中断状态时，执行推出操作
                System.out.println("通过this.isInterrupted()检测到中断");
                System.out.println("第一个interrupted()"+Thread.interrupted());
                System.out.println("第二个interrupted()"+Thread.interrupted());
                break;
            }
        }
    }
}

输出结果：通过this.isInterrupted()检测到中断第一个interrupted()true 第二个interrupted()false

线程抛出InterruptedException异常时，会重置中断标记位为false，需再次调用interrupt()方法才可推出循环

public class HasInterruptException {

    public static void main(String[] args) throws InterruptedException {
        MyThread myThread = new MyThread("my-thread");
        myThread.start();
        Thread.sleep(500);
        myThread.interrupt();
    }


    private static class MyThread extends Thread {

        public MyThread(String name) {
            super(name);
        }

        @Override
        public void run() {
            Thread thread = Thread.currentThread();
            while (!thread.isInterrupted()) {
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                    System.out.println("抛出异常， " + thread.getName() + " interrupt flag is " + thread.isInterrupted());
                    // 当线程抛出InterruptedException异常时，会重置中断标记位为false，需再次调用interrupt()方法才可推出循环
                    thread.interrupt();
                }
                System.out.println(thread.getName() + "运行中...");
            }
            System.out.println("跳出循环后" + thread.getName() + " interrupt flag is " + thread.isInterrupted());
        }
    }
}

输出结果 my-thread运行中... my-thread运行中... my-thread运行中... my-thread运行中... java.lang.InterruptedException: sleep interrupted at java.lang.Thread.sleep(Native Method) at com.shawntime.enjoy.concurrency.interrupt.HasInterruptException$MyThread.run(HasInterruptException.java:24) 抛出异常， my-thread interrupt flag is false my-thread运行中... 跳出循环后my-thread interrupt flag is true

结论

当抛出InterruptedException异常时，中断标记位被重置为false