通常我们会有这样的需求，即停止一个线程。在java的api中有stop、suspend等方法可以达到目的，但由于这些方法在使用上存在不安全性，会带来不好的副作用，不建议被使用。具体原因可以参考Why is Thread.stop deprecated。
在本文中，将讨论中断在java中的使用。
中断在java中主要有3个方法，interrupt(),isInterrupted()和interrupted()。
接下来，看看具体在代码中如何使用。
interrupt()不能中断在运行中的线程，它只能改变中断状态而已。
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public class InterruptionInJava implements Runnable{ public static void main(String[] args) throws InterruptedException { Thread testThread = new Thread(new InterruptionInJava(),"InterruptionInJava"); //start thread testThread.start(); Thread.sleep(1000); //interrupt thread testThread.interrupt(); System.out.println("main end"); } @Override public void run() { while(true){ if(Thread.currentThread().isInterrupted()){ System.out.println("Yes,I am interruted,but I am still running"); }else{ System.out.println("not yet interrupted"); } } }} |
结果显示，被中断后，仍旧运行，不停打印Yes,I am interruted,but I am still running
那么，如何正确中断？
既然是只能修改中断状态，那么我们应该针对中断状态做些什么。
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public class InterruptionInJava implements Runnable{ public static void main(String[] args) throws InterruptedException { Thread testThread = new Thread(new InterruptionInJava(),"InterruptionInJava"); //start thread testThread.start();// Thread.sleep(1000); //interrupt thread testThread.interrupt(); System.out.println("main end"); } @Override public void run() { while(true){ if(Thread.currentThread().isInterrupted()){ System.out.println("Yes,I am interruted,but I am still running"); return; }else{ System.out.println("not yet interrupted"); } } }} |
修改代码，在状态判断中如上，添加一个return就okay了。但现实中，我们可能需要做的更通用，不禁又要发出天问，如何中断线程？答案是添加一个开关。
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public class InterruptionInJava implements Runnable{ private volatile static boolean on = false; public static void main(String[] args) throws InterruptedException { Thread testThread = new Thread(new InterruptionInJava(),"InterruptionInJava"); //start thread testThread.start(); Thread.sleep(1000); InterruptionInJava.on = true; System.out.println("main end"); } @Override public void run() { while(!on){ if(Thread.currentThread().isInterrupted()){ System.out.println("Yes,I am interruted,but I am still running"); }else{ System.out.println("not yet interrupted"); } } }} |
会输出类似结果，这表明是成功中断了的：
这种开关的方式看起来包治百病，但是当遇到线程阻塞时，就会很无奈了，正如下面代码所示：
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public class InterruptionInJava implements Runnable{ private volatile static boolean on = false; public static void main(String[] args) throws InterruptedException { Thread testThread = new Thread(new InterruptionInJava(),"InterruptionInJava"); //start thread testThread.start(); Thread.sleep(1000); InterruptionInJava.on = true; System.out.println("main end"); } @Override public void run() { while(!on){ try { Thread.sleep(10000000); } catch (InterruptedException e) { System.out.println("caught exception: "+e); } } }} |
线程被阻塞无法被中断。这时候救世主interrupt函数又回来了，它可以迅速中断被阻塞的线程，抛出一个InterruptedException，把线程从阻塞状态中解救出来,show the code。
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public class InterruptionInJava implements Runnable{ private volatile static boolean on = false; public static void main(String[] args) throws InterruptedException { Thread testThread = new Thread(new InterruptionInJava(),"InterruptionInJava"); //start thread testThread.start(); Thread.sleep(1000); InterruptionInJava.on = true; testThread.interrupt(); System.out.println("main end"); } @Override public void run() { while(!on){ try { Thread.sleep(10000000); } catch (InterruptedException e) { System.out.println("caught exception right now: "+e); } } }} |
结果截图，达到预期。
这种情形同样适用io阻塞，通常io阻塞会立即抛出一个SocketException，类似于上面说的InterruptedException。
原文：https://www.cnblogs.com/cxhfuujust/p/10757842.html