Java interrupt 中断

为什么要中断？

根据需要停止某些持续的方法，这些方法可以被中断，所以又被称为可中断方法，包括：

Object的wait(), wait(long), wait(long, int)，

Thraed的sleep(long), sleep(long, int), join(), join(long), join(long, int)，

InterruptibleChannel的io操作，

Selector的wakeup方法，

其他方法。

如何中断？

Thread的三个方法：

方法	功能	特点
public void interrupt()	中断当前线程	更新中断标记为true，抛出InterruptedException
public void static boolean isInterrupted()	检查线程中断标记	返回查中断标记,可用于判断是否被调用中断
public boolean interrupted()	检查线程中断标记,可能更新	返回中断标记，若为true则更新为false。

当线程被中断时，会将中断标记置为true，并抛出InterruptedException异常，当捕获到这个异常时，说明当前线程的中断方法被调用。

如果在可中断方法执行前，调用了interrupt()方法，那么当执行到可中断方法时，会立刻抛出InterruptedException。

线程中catch (InterruptedException ex)会导致中断标志被擦除。

示例

interrupt:

public static void main(String[] args) throws InterruptedException {

        Thread thread = new Thread() {
            @Override
            public void run() {
                while (true) {
                    try {
                        TimeUnit.MINUTES.sleep(2);
                    } catch (InterruptedException ex) {
                        System.out.println("I am interrupted");

                    }

                }
            }
        };

        thread.start();
        TimeUnit.MICROSECONDS.sleep(2);
        thread.interrupt();
}

output:
I am interrupted

interrupted：

public static void main(String[] args) throws InterruptedException {

        Thread thread = new Thread() {
            @Override
            public void run() {
                while (true) {
                    //移除sleep和try-catch,因为可中断方法中断时，会将中断标志置为false
                }
            }
        };

        thread.start();
        TimeUnit.MICROSECONDS.sleep(2);
        System.out.println("before invoke interrupte,thread is interrupted:" + thread.isInterrupted());
        thread.interrupt();
        System.out.println("after invoke interrupte is interrupted:" + thread.isInterrupted());       
}

output:
before invoke interrupte,thread is interrupted:false
after invoke interrupte is interrupted:true

iterrupted

public static void main(String[] args) throws InterruptedException {

        Thread thread = new Thread() {
            @Override
            public void run() {
                while (true) {
                    System.out.println("thread is interrupted:" + Thread.interrupted());
                }
            }
        };
        thread.setDaemon(true);
        thread.start();
        TimeUnit.MICROSECONDS.sleep(2);
        System.out.println("before invoke interrupte,thread is interrupted:" + thread.isInterrupted());
        thread.interrupt();
        System.out.println("after invoke interrupte is interrupted:" + thread.isInterrupted());
        TimeUnit.MICROSECONDS.sleep(1);
        System.out.println("finally thread is interrupted:" + thread.isInterrupted());

    }

输出：

output:
thread is interrupted:false
before invoke interrupte,thread is interrupted:false
thread is interrupted:false
after invoke interrupte is interrupted:true
thread is interrupted:true
thread is interrupted:false
finally thread is interrupted:false

可中断方法执行前调用interrupt

public static void main(String[] args) {

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

        Thread.currentThread().interrupt();
        System.out.println("after interrupt,do something...");
        try {
            TimeUnit.MICROSECONDS.sleep(2);
        }
        catch (InterruptedException e) {
            System.out.println("thread is interrupted:" + Thread.currentThread().isInterrupted());
        }
    }

输出：

thread is interrupted:false

after interrupt,do something...

thread is interrupted:false