[TOC]

Thread類的interrupt方法倒是見過好幾次，但是一直不知道他的具體是干什么的，今天查了以下api和core java大概解決了自己的疑惑。(順便吐槽一下core java的翻譯，問題實(shí)在不少)

一、關(guān)于interrupt state

There is boolean flag in every thread that indicating the interrupt state,When the interrupt method is called on a thread, the interrupted status of the thread is set. --core java
每個(gè)線程都有一個(gè)布爾變量表示線程的中斷狀態(tài),當(dāng)線程調(diào)用interrupt后，線程的中斷狀態(tài)會(huì)設(shè)置.
另外，中斷狀態(tài) 可以通過線程的isInterrupted()返回值來判定，true表示設(shè)置為中斷狀態(tài)，false表示非中斷狀態(tài)；
The interrupt method can be used to request termination of a thread.　　　--core java
interrupt方法可以請(qǐng)求中斷一個(gè)線程(也就是說只是請(qǐng)求中斷，并不能直接中斷).

以下代碼驗(yàn)證了上述結(jié)論，可以看到程序的輸出會(huì)出現(xiàn)這種情況：首先為false，interrupt以后，變?yōu)閠rue，但是程序依舊會(huì)輸出0到9；

private void simpleInterrupt() {
    Thread t = new Thread(){
        @Override
        public void run() {
            for (int i = 0; i < 10; i++) {
                System.out.println(i);
            }
        }
    };

    t.start();
    System.out.println("before interrupt:" + t.isInterrupted());
    t.interrupt();
    System.out.println("after interrupt:" + t.isInterrupted());
}

由此可見，interrupt并不像它的中文意思中斷一樣能中斷線程，但是改變了isInterrupted方法的返回值，這個(gè)還是可以作為run方法的循環(huán)結(jié)束的條件，從而中斷線程，代碼如下：

private void simpleInterruptAffect() {
    Thread t = new Thread(){
        @Override
        public void run() {
            for (int i = 0; i < 100 && !isInterrupted(); i++) {
                System.out.println(i);
            }
        }
    };

    t.start();
    try {
        Thread.sleep(5);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    t.interrupt();
}

多運(yùn)行幾遍，發(fā)現(xiàn)i沒到99就結(jié)束了。

二、sleep、wait等方法和interrupt的聯(lián)系

1. 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.　　--doc
當(dāng)線程由于sleep或者wait等方法阻塞時(shí)，如果調(diào)用了interrupt方法，就會(huì)拋出一個(gè)異常（補(bǔ)充：core java上說是由于系統(tǒng)無法檢測(cè)處于阻塞狀態(tài)線程的interrupt state），并且清除掉線程的interrupt status（使得isInterrupted方法返回false），用代碼驗(yàn)證一下：

 private void interruptSleep() {
   Thread t1 = new Thread() {
           @Override
           public void run() {
               try {
                Thread.sleep(1000);
                } catch (InterruptedException e) {
                System.out.println("interrupt status in catch:" + isInterrupted());
                }
            }
    };
    t1.start();
    System.out.println("interrupt status before interrupt:" + t1.isInterrupted());
    t1.interrupt();
    System.out.println("interrupt status after interrupt:" + t1.isInterrupted());

}

一般會(huì)依次輸出
interrupt status before interrupt:false
interrupt status after interrupt:true
interrupt status in catch:false
2. 線程不能睡眠的原因
If you call the sleep method when the interrupted status is set, it doesn’t sleep. Instead, it
clears the status and throws an InterruptedException.
如果線程睡眠前線程它的isInterrupted返回true，線程就不會(huì)睡眠，相反，線程的會(huì)清除掉interrupt status并且拋出一個(gè)異常。同樣用代碼驗(yàn)證一下。

volatile boolean flag = false;
private void interruptThenSleep() {

    Thread t = new Thread(){
        @Override
        public void run() {
            while(!flag){}
            try {
                Thread.sleep(10000);
            } catch (InterruptedException e) {
                System.out.println("interrupt status in catch:" + isInterrupted());
            }
        }
    };

    t.start();
    t.interrupt();
    System.out.println("interrupt status after interrupt:" + t.isInterrupted());
    flag = true;

}

t線程不會(huì)休眠10s
并且輸出：
interrupt status after interrupt:true
interrupt status in catch:false
到這里可也以得出結(jié)論：只要線程的isInterrupted()返回true，Thread.sleep()都會(huì)拋出異常，并且清除線程的中斷狀態(tài)。

3.關(guān)于interrupted
Tests whether the current thread has been interrupted. The interrupted status of the thread is cleared by this method. 　--doc

檢測(cè)當(dāng)前線程是否處于中斷狀態(tài)，調(diào)用后中斷狀態(tài)會(huì)重置(狀態(tài)變量變?yōu)閒alse)

同樣驗(yàn)證一下

package com.basic;

/**
 * Created by liouville on 3/25/16.
 */
public class CompareInterrupt {

    volatile static  boolean flag = true;
    public static void main(String[] args) {

        MyThread t = new MyThread();
        t.start();

        System.out.println("主線程：" + t.isInterrupted());
        t.interrupt();

        flag = false;
    }

    private static class MyThread extends Thread{
        @Override
        public void run() {
            super.run();
            System.out.println("run...");

            while (flag){yield();}
            System.out.println(isInterrupted());
            System.out.println(interrupted());
            System.out.println(isInterrupted());
        }
    }
}

一般輸出：
主線程：false
run...
true
true
false

三、interrupt interrupted isInterrupted

現(xiàn)在可以更清晰的看到三者之間的區(qū)別。
interrupt用來請(qǐng)求中斷線程，但是只是設(shè)置一下線程的中斷狀態(tài)的標(biāo)記變量，并不會(huì)直接中斷線程。
isInterrupted用來判斷調(diào)用該方法的線程是否處于中斷狀態(tài)，處于中斷狀態(tài)返回true,否則false;，不會(huì)影響這個(gè)中斷狀態(tài)標(biāo)記變量的值。
interrupted是一個(gè)靜態(tài)方法，也是用來檢測(cè)當(dāng)前線程是否處于中斷狀態(tài)，處于中斷狀態(tài)返回true,否則false，但是它會(huì)重置中斷狀態(tài)的標(biāo)記變量為false.**