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用interrupt()中断Java线程

发布时间：2024/4/17 java 69 豆豆
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http://hapinwater.iteye.com/blog/310558

最近在学习Java线程相关的东西，和大家分享一下，有错误之处欢迎大家指正．

假如我们有一个任务如下，交给一个Java线程来执行，如何才能保证调用interrupt()来中断它呢？

Java代码
  • class ATask implements Runnable{ 
  •  
  •     private double d = 0.0; 
  •      
  •     public void run() { 
  •         //死循环执行打印"I am running!" 和做消耗时间的浮点计算 
  •         while (true) { 
  •             System.out.println("I am running!"); 
  •              
  •             for (int i = 0; i < 900000; i++) { 
  •                 d =  d + (Math.PI + Math.E) / d; 
  •             } 
  •             //给线程调度器可以切换到其它进程的信号 
  •             Thread.yield(); 
  •         } 
  •     } 
  • } 
  •  
  • public class InterruptTaskTest { 
  •      
  •     public static void main(String[] args) throws Exception{ 
  •         //将任务交给一个线程执行 
  •         Thread t = new Thread(new ATask()); 
  •         t.start(); 
  •          
  •         //运行一断时间中断线程 
  •         Thread.sleep(100); 
  •         System.out.println("****************************"); 
  •         System.out.println("Interrupted Thread!"); 
  •         System.out.println("****************************"); 
  •         t.interrupt(); 
  •     } 
  • }  
    • class ATask implements Runnable{private double d = 0.0;public void run() {//死循环执行打印"I am running!" 和做消耗时间的浮点计算while (true) {System.out.println("I am running!");for (int i = 0; i < 900000; i++) {d = d + (Math.PI + Math.E) / d;}//给线程调度器可以切换到其它进程的信号Thread.yield();}} }public class InterruptTaskTest {public static void main(String[] args) throws Exception{//将任务交给一个线程执行Thread t = new Thread(new ATask());t.start();//运行一断时间中断线程Thread.sleep(100);System.out.println("****************************");System.out.println("Interrupted Thread!");System.out.println("****************************");t.interrupt();} }



    运行这个程序，我们发现调用interrupt()后，程序仍在运行，如果不强制结束，程序将一直运行下去，如下所示:

    Java代码
  • ...... 
  • I am running! 
  • I am running! 
  • I am running! 
  • I am running! 
  • **************************** 
  • Interrupted Thread! 
  • **************************** 
  • I am running! 
  • I am running! 
  • I am running! 
  • I am running! 
  • I am running! 
  • .... 
    • ...... I am running! I am running! I am running! I am running! **************************** Interrupted Thread! **************************** I am running! I am running! I am running! I am running! I am running! ....


    虽然中断发生了，但线程仍然在进行，离开线程有两种常用的方法：
    抛出InterruptedException和用Thread.interrupted()检查是否发生中断,下面分别看一下这两种方法：
    1.在阻塞操作时如Thread.sleep()时被中断会抛出InterruptedException(注意，进行不能中断的IO操作而阻塞和要获得对象的锁调用对象的synchronized方法而阻塞时不会抛出InterruptedException)

    Java代码
  • class ATask implements Runnable{ 
  •  
  •     private double d = 0.0; 
  •      
  •     public void run() { 
  •         //死循环执行打印"I am running!" 和做消耗时间的浮点计算 
  •         try { 
  •             while (true) { 
  •                 System.out.println("I am running!"); 
  •                  
  •                 for (int i = 0; i < 900000; i++) { 
  •                     d =  d + (Math.PI + Math.E) / d; 
  •                 } 
  •                 //休眠一断时间,中断时会抛出InterruptedException 
  •                 Thread.sleep(50); 
  •             } 
  •         } catch (InterruptedException e) { 
  •             System.out.println("ATask.run() interrupted!"); 
  •         } 
  •     } 
  • } 
    • class ATask implements Runnable{private double d = 0.0;public void run() {//死循环执行打印"I am running!" 和做消耗时间的浮点计算try {while (true) {System.out.println("I am running!");for (int i = 0; i < 900000; i++) {d = d + (Math.PI + Math.E) / d;}//休眠一断时间,中断时会抛出InterruptedExceptionThread.sleep(50);}} catch (InterruptedException e) {System.out.println("ATask.run() interrupted!");}} }


    程序运行结果如下:

    Java代码
  • I am running! 
  • I am running! 
  • **************************** 
  • Interrupted Thread! 
  • **************************** 
  • ATask.run() interrupted! 
    • I am running! I am running! **************************** Interrupted Thread! **************************** ATask.run() interrupted!


    可以看到中断任务时让任务抛出InterruptedException来离开任务．

    2.Thread.interrupted()检查是否发生中断.Thread.interrupted()能告诉你线程是否发生中断,并将清除中断状态标记，所以程序不会两次通知你线程发生了中断．

    Java代码
  • class ATask implements Runnable{ 
  •  
  •     private double d = 0.0; 
  •      
  •     public void run() { 
  •          
  •         //检查程序是否发生中断 
  •         while (!Thread.interrupted()) { 
  •             System.out.println("I am running!"); 
  •  
  •             for (int i = 0; i < 900000; i++) { 
  •                 d = d + (Math.PI + Math.E) / d; 
  •             } 
  •         } 
  •  
  •         System.out.println("ATask.run() interrupted!"); 
  •     } 
  • } 
    • class ATask implements Runnable{private double d = 0.0;public void run() {//检查程序是否发生中断while (!Thread.interrupted()) {System.out.println("I am running!");for (int i = 0; i < 900000; i++) {d = d + (Math.PI + Math.E) / d;}}System.out.println("ATask.run() interrupted!");} }


    程序运行结果如下：

    Java代码
  • I am running! 
  • I am running! 
  • I am running! 
  • I am running! 
  • I am running! 
  • I am running! 
  • I am running! 
  • **************************** 
  • Interrupted Thread! 
  • **************************** 
  • ATask.run() interrupted! 
    • I am running! I am running! I am running! I am running! I am running! I am running! I am running! **************************** Interrupted Thread! **************************** ATask.run() interrupted!



    我们可结合使用两种方法来达到可以通过interrupt()中断线程.请看下面例子:

    Java代码
  • class ATask implements Runnable{ 
  •  
  •     private double d = 0.0; 
  •      
  •     public void run() { 
  •          
  •         try { 
  •         //检查程序是否发生中断 
  •         while (!Thread.interrupted()) { 
  •             System.out.println("I am running!"); 
  •             //point1 before sleep 
  •             Thread.sleep(20); 
  •             //point2 after sleep 
  •             System.out.println("Calculating"); 
  •             for (int i = 0; i < 900000; i++) { 
  •                 d = d + (Math.PI + Math.E) / d; 
  •             } 
  •         } 
  •          
  •         } catch (InterruptedException e) { 
  •             System.out.println("Exiting by Exception"); 
  •         } 
  •          
  •         System.out.println("ATask.run() interrupted!"); 
  •     } 
  • } 
    • class ATask implements Runnable{private double d = 0.0;public void run() {try {//检查程序是否发生中断while (!Thread.interrupted()) {System.out.println("I am running!");//point1 before sleepThread.sleep(20);//point2 after sleepSystem.out.println("Calculating");for (int i = 0; i < 900000; i++) {d = d + (Math.PI + Math.E) / d;}}} catch (InterruptedException e) {System.out.println("Exiting by Exception");}System.out.println("ATask.run() interrupted!");} }


    在point1之前处point2之后发生中断会产生两种不同的结果，可以通过修改InterruptTaskTest main()里的Thread.sleep()的时间来达到在point1之前产生中断或在point2之后产生中断.
    如果在point1之前发生中断，程序会在调用Thread.sleep()时抛出InterruptedException从而结束线程．这和在Thread.sleep()时被中断是一样的效果.程序运行结果可能如下：

    Java代码
  • I am running! 
  • Calculating 
  • I am running! 
  • Calculating 
  • I am running! 
  • Calculating 
  • I am running! 
  • **************************** 
  • Interrupted Thread! 
  • **************************** 
  • Exiting by Exception 
  • ATask.run() interrupted! 
    • I am running! Calculating I am running! Calculating I am running! Calculating I am running! **************************** Interrupted Thread! **************************** Exiting by Exception ATask.run() interrupted!


    如果在point2之后发生中断，线程会继续执行到下一次while判断中断状态时．程序运行结果可能如下：

    Java代码
  • I am running! 
  • Calculating 
  • I am running! 
  • Calculating 
  • I am running! 
  • Calculating 
  • **************************** 
  • Interrupted Thread! 
  • **************************** 
  • ATask.run() interrupted! 

    •  

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