用interrupt()中断Java线程

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

1. class ATask implements Runnable{ 
2.  
3.     private double d =0.0; 
4.      
5.     public void run() { 
6.         //死循环执行打印"I am running!" 和做消耗时间的浮点计算 
7.         while (true) { 
8.             System.out.println("I am running!"); 
9.              
10.             for (int i =0; i < 900000; i++) { 
11.                 d =  d + (Math.PI + Math.E) / d; 
12.             } 
13.             //给线程调度器可以切换到其它进程的信号 
14.             Thread.yield(); 
15.         } 
16.     } 
17. } 
18.  
19. public class InterruptTaskTest { 
20.      
21.     public staticvoid main(String[] args) throws Exception{ 
22.         //将任务交给一个线程执行 
23.         Thread t = new Thread(new ATask()); 
24.         t.start(); 
25.          
26.         //运行一断时间中断线程 
27.         Thread.sleep(100); 
28.         System.out.println("****************************"); 
29.         System.out.println("Interrupted Thread!"); 
30.         System.out.println("****************************"); 
31.         t.interrupt(); 
32.     } 
33. }  

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

1. ...... 
2. I am running! 
3. I am running! 
4. I am running! 
5. I am running! 
6. **************************** 
7. Interrupted Thread! 
8. **************************** 
9. I am running! 
10. I am running! 
11. I am running! 
12. I am running! 
13. I am running! 
14. .... 

......
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

1. class ATask implements Runnable{ 
2.  
3.     private double d =0.0; 
4.      
5.     public void run() { 
6.         //死循环执行打印"I am running!" 和做消耗时间的浮点计算 
7.         try { 
8.             while (true) { 
9.                 System.out.println("I am running!"); 
10.                  
11.                 for (int i =0; i < 900000; i++) { 
12.                     d =  d + (Math.PI + Math.E) / d; 
13.                 } 
14.                 //休眠一断时间,中断时会抛出InterruptedException 
15.                 Thread.sleep(50); 
16.             } 
17.         } catch (InterruptedException e) { 
18.             System.out.println("ATask.run() interrupted!"); 
19.         } 
20.     } 
21. } 

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

1. I am running! 
2. I am running! 
3. **************************** 
4. Interrupted Thread! 
5. **************************** 
6. 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

1. class ATask implements Runnable{ 
2.  
3.     private double d =0.0; 
4.      
5.     public void run() { 
6.          
7.         //检查程序是否发生中断 
8.         while (!Thread.interrupted()) { 
9.             System.out.println("I am running!"); 
10.  
11.             for (int i =0; i < 900000; i++) { 
12.                 d = d + (Math.PI + Math.E) / d; 
13.             } 
14.         } 
15.  
16.         System.out.println("ATask.run() interrupted!"); 
17.     } 
18. } 

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

1. I am running! 
2. I am running! 
3. I am running! 
4. I am running! 
5. I am running! 
6. I am running! 
7. I am running! 
8. **************************** 
9. Interrupted Thread! 
10. **************************** 
11. 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

1. class ATask implements Runnable{ 
2.  
3.     private double d =0.0; 
4.      
5.     public void run() { 
6.          
7.         try { 
8.         //检查程序是否发生中断 
9.         while (!Thread.interrupted()) { 
10.             System.out.println("I am running!"); 
11.             //point1 before sleep 
12.             Thread.sleep(20); 
13.             //point2 after sleep 
14.             System.out.println("Calculating"); 
15.             for (int i =0; i < 900000; i++) { 
16.                 d = d + (Math.PI + Math.E) / d; 
17.             } 
18.         } 
19.          
20.         } catch (InterruptedException e) { 
21.             System.out.println("Exiting by Exception"); 
22.         } 
23.          
24.         System.out.println("ATask.run() interrupted!"); 
25.     } 
26. } 

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

1. I am running! 
2. Calculating 
3. I am running! 
4. Calculating 
5. I am running! 
6. Calculating 
7. I am running! 
8. **************************** 
9. Interrupted Thread! 
10. **************************** 
11. Exiting by Exception 
12. 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

1. I am running! 
2. Calculating 
3. I am running! 
4. Calculating 
5. I am running! 
6. Calculating 
7. **************************** 
8. Interrupted Thread! 
9. **************************** 
10. ATask.run() interrupted!