Thread interrupt

线程中断有3个重要的方法：
thread.interrupt() 给目标线程发送中断信号，目标线程中断标记置为true.
thread.isInterrupted() 返回目标线程的中断标记
thread.interrupted() 返回目标线程的中断标记，并将其置为false。

调用Thread.interrupt() 用于请求另外一个线程中止执行，而不是直接中止
调用线程的interrupt方法，只有当线程走到了sleep, wait, join等阻塞这些方法的时候，才会抛出InterruptedException

package test;

public class Sys extends Thread {
    private boolean stop = false;

    public static void main(String[] args) throws InterruptedException {
        Sys thread = new Sys();
        thread.start();
        Thread.sleep(3000);
        thread.interrupt();
        Thread.sleep(3000);
        System.out.println("Stopping application");
    }

    @Override
    public void run() {
        while (!stop) {
            System.out.println("Thread is running ... ");
        }

        System.out.println("Thread exiting under request");
    }
}

线程被发送了中断信号，但是没有逻辑去处理这段信号。所以线程会一直运行。

package test;

public class Sys extends Thread {
    private boolean stop = false;

    public static void main(String[] args) throws InterruptedException {
        Sys thread = new Sys();
        thread.start();
        Thread.sleep(3000);
        thread.interrupt();
        Thread.sleep(3000);
        System.out.println("Stopping application");
    }

    @Override
    public void run() {
        while (!stop) {
            System.out.println("Thread is running ... ");
            if (Thread.currentThread().isInterrupted()) { // 处理线程中断的逻辑
                break;
            }
        }

        System.out.println("Thread exiting under request");
    }
}

Thread is running ...
Thread is running ...
...........
Thread is running ...
Thread is running ...
Thread exiting under request
Stopping application

通过判断是否有中断信号则能中断成功

package test;

public class Sys extends Thread {
    private boolean stop = false;

    public static void main(String[] args) throws InterruptedException {
        Sys thread = new Sys();
        thread.start();
        Thread.sleep(3000);
        thread.interrupt();
        Thread.sleep(3000);
        System.out.println("Stopping application");
    }

    @Override
    public void run() {
        while (!stop) {
            System.out.println("Thread is running ... ");
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                System.out.println("Exception:" + e.getMessage());
                if(Thread.currentThread().isInterrupted()){ // 处理线程中断的逻辑
                    break;
                }
            }
        }

        System.out.println("Thread exiting under request");
    }
}

Thread is running ...
Thread is running ...
Exception:sleep interrupted
Thread is running ...
Thread is running ...
Stopping application
Thread is running ...
Thread is running ...
......

打印中断后继续执行。

原因：sleep()函数执行时，若线程被中断，会抛出中断异常，并且中断符号位会清除（置false）

 * @throws  InterruptedException
 *          if any thread has interrupted the current thread. The
 *          <i>interrupted status</i> of the current thread is
 *          cleared when this exception is thrown.
 */
public static native void sleep(long millis) throws InterruptedException;