什么是线程中断

java中的线程中断并不是指强制线程中断执行,而是指调用线程中断起到一个通知作用,让线程知道自己被中断了.至于线程是否应该继续执行下去,这个取决于业务代码本身.而原来提供的stop()方法,因为固有不安全性,现在已经不推荐使用该方式来实现线程中断.

线程中断相关方法

    public void interrupt()

该方法作用就是中断线程.线程的中断标志将被标记为已中断.

    public boolean isInterrupted()

该方法作用是检测线程是否已经中断.线程的中断状态不受该方法影响.

    public static boolean interrupted() {
        return currentThread().isInterrupted(true);
    }

该方法同样也是用来检测线程是否中断的.但是需要注意的是,该方法会清除线程的中断状态.如果多次调用该方法.第一次返回true,那么从第二次开始该方法将返回false.具体实现代码如下:

private native boolean isInterrupted(boolean ClearInterrupted);

线程中断实战

线程收到中断信号,业务代码未处理中断失败

public class App1 {

    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(() -> {
            while (true){
                Thread thread = Thread.currentThread();
                boolean result = thread.isInterrupted();
                System.out.println(String.format("当前线程:[%s],中断状态:[%b]",thread.getName(),result));
            }
        });
        t1.setName("t1");
        t1.start();
        Thread.sleep(1000);
        t1.interrupt();
    }
}

上面代码的刚开始打印的结果为:当前线程:[t1],中断状态:[false],过1秒后结果打印当前线程:[t1],中断状态:[true],但是线程并没有停止运行.这正好说明了之前说的,java中的线程中断只是一个通知作用,并不会强制线程停止执行.

线程收到中断信号,业务代码处理了中断信号中断成功

public class App1 {

    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(() -> {
            while (true){
                Thread thread = Thread.currentThread();
                boolean result = thread.isInterrupted();
                System.out.println(String.format("当前线程:[%s],中断状态:[%b]",thread.getName(),result));
                if (result){
                    break;
                }
            }
        });
        t1.setName("t1");
        t1.start();
        Thread.sleep(1000);
        t1.interrupt();
    }
}

上面代码的刚开始打印的结果为:当前线程:[t1],中断状态:[false],过1秒后结果打印当前线程:[t1],中断状态:[true],而且该语句只会打印一次,然后程序停止运行.

线程处于WAITING或TIMED_WAITING下,业务代码未处理InterruptedException导致中断失败

public class App1 {

    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(() -> {
            while (true){
                Thread thread = Thread.currentThread();
                try {
                    Thread.sleep(3000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                boolean result = thread.isInterrupted();
                System.out.println(String.format("当前线程:[%s],中断状态:[%b]",thread.getName(),result));
                if (result){
                    break;
                }
            }
        });
        t1.setName("t1");
        t1.start();
        Thread.sleep(1000);
        System.out.println("t1.getState() = " + t1.getState());
        t1.interrupt();
    }
}

上面的代码打印结果如下:

java.lang.InterruptedException: sleep interrupted
    at java.lang.Thread.sleep(Native Method)
    at com.buydeem.aqs.App1.lambda$main$0(App1.java:13)
    at java.lang.Thread.run(Thread.java:745)
t1.getState() = TIMED_WAITING
当前线程:[t1],中断状态:[false]
当前线程:[t1],中断状态:[false]

线程处于TIMED_WAITING状态下,然后发送中断信号.处理TIMED_WAITING将抛出中断异常InterruptedException,同时还会清除中断状态.最后会一直打印当前线程:[t1],中断状态:[false],导致中断失败.

线程处于WAITING或TIMED_WAITING下,业务代码处理InterruptedException中断成功

public class App1 {

    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(() -> {
            while (true){
                Thread thread = Thread.currentThread();
                try {
                    Thread.sleep(3000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                    System.out.println("收到中断异常,退出线程执行");
                    break;
                }
                boolean result = thread.isInterrupted();
                System.out.println(String.format("当前线程:[%s],中断状态:[%b]",thread.getName(),result));
                if (result){
                    break;
                }
            }
        });
        t1.setName("t1");
        t1.start();
        Thread.sleep(1000);
        System.out.println("t1.getState() = " + t1.getState());
        t1.interrupt();
    }
}