用interrupt()中断Java线程-优快云博客

本文探讨了Java中如何通过调用interrupt()方法中断线程，并分析了两种常见中断方法：抛出InterruptedException和使用Thread.interrupted()检查中断状态。

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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InterruptedException

      Thread.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 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!");

  }

}

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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