线程的interrupt()

官网解释

If this thread is blocked in an invocation of the wait(), wait(long), or wait(long, int) methods of the Object class, or of the join(), join(long), join(long, int), sleep(long), or sleep(long, int), methods of this class, then its interrupt status will be cleared and it will receive an InterruptedException.

意思是当线程被blocked的时候可以被打断，wait()、sleep()、join()时被打断会抛出InterruptedException异常。

演示sleep()被打断

        Thread t1 = new Thread() {
            @Override
            public void run() {
                while (true) {
                    System.out.println("running...");
                    try {
                        Thread.sleep(100L);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                        break;
                    }
                }
            }
        };

        t1.start();
        Thread.sleep(100L);
        System.out.println(t1.isInterrupted());
        t1.interrupt();
        System.out.println(t1.isInterrupted());

在sleep()被打断在异常中要执行break;打断循环，否则该循环一直在执行

演示wait()被打断

package com.dwz.concurrency.chapter6;

public class ThreadInterrupt {
    private static final Object MONITOR = new Object();
    public static void main(String[] args) throws InterruptedException {
        Thread t2 = new Thread() {
            @Override
            public void run() {
                while (true) {
                    System.out.println("running...");
                    synchronized (MONITOR) {
                        try {
                            MONITOR.wait(100L);
                        } catch (InterruptedException e) {
                            System.out.println("收到打断信号。。。");
                            e.printStackTrace();
                            break;
                        }
                    }
                }
            }
        };

        t2.start();
        Thread.sleep(100L);
        System.out.println(t2.isInterrupted());
        t2.interrupt();
        System.out.println(t2.isInterrupted());
    }
}

1.跟sleep()一样，wait()被打断时在异常中要执行break;打断循环，否则该循环一直在执行

2.wait()的调用者一定是一个对象

演示join()被打断

package com.dwz.concurrency.chapter6;

public class ThreadInterrupt3 {
    public static void main(String[] args) throws InterruptedException  {
        Thread main = Thread.currentThread();
        Thread t1 = new Thread() {
            @Override
            public void run() {
                while (true) {

　　　　　　　　　　 　　System.out.println(Thread.currentThread().getName());
　　　　　　　　　　　　 System.err.println(Thread.currentThread().isInterrupted());

                }
            }
        };

        t1.start();
        
        System.out.println("main: " + main.getName());
        Thread t2 = new Thread() {
            @Override
            public void run() {
                try {
                    Thread.sleep(1000L);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("t2: " + Thread.currentThread().getName());
                main.interrupt();
                System.out.println("interrupt...");
            }
        };
        t2.start();
        
        try {
            t1.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
            t1.interrupt();
        }
        
        System.out.println("main isInterrupted:" + main.isInterrupted());
        System.out.println("t1 isInterrupted:" + t1.isInterrupted());
        while(!t1.isInterrupted()) {
            Thread.sleep(1000L);
            System.out.println(t1.isInterrupted());
        }
    }
}

1.我们要清楚，join的对象是main线程，要想打断 t1.join(), 要在另一个线程中执行 main.interrupt()

2.isInterrupted()表示线程是否被打断，如果只执行 main.interrupt() 方法，意味着 t1.join()被打断，t1仍是未打断的，执行 t1.interrupt()才会改变t1状态

3. t1.join() 一定要在 t1.start() 和  t2.start() 之后被执行。