线程方法 isInterrupted

喜欢ヅ旅行 2024-03-16 11:34 29阅读 0赞

### isInterrupted ###

<table> 
 <thead> 
  <tr> 
   <th align="left">isInterrupted是Thread的一个成员方法，它主要<code>判断当前线程是否被中断</code>，该方法仅仅是对interrupt标识的一个判断，并不会影响标识发生任何改变</th> 
  </tr> 
 </thead> 
</table>

public class ThreadisInterrupted {
        
        public static void main(String[] args) throws InterruptedException {
        
            Thread thread = new Thread(() -> {
        
                while (true) {
        
                //do nothing, just empty loop.
                }
            });
            thread.start();
    
            TimeUnit.MILLISECONDS.sleep(2);
    
            System.out.printf("Thread is interrupted ? %s\n", thread.isInterrupted());
            thread.interrupt();
            System.out.printf("Thread is interrupted ? %s\n", thread.isInterrupted());
        }
    }

<table> 
 <thead> 
  <tr> 
   <th align="left">上面的代码中定义了一个线程，并且在线程的执行单元中（run方法）写了一个空的死循环，<code>为什么不写sleep呢？</code>因为sleep是可中断方法，会捕获到中断信号，从而干扰我们程序的结果。下面是程序运行的结果，记得手动结束上面的程序运行，或者你也可以将上面定义的线程指定为守护线程，这样就会随着主线程的结束导致JVM中没有非守护线程而自动退出。</th> 
  </tr> 
 </thead> 
</table>

Thread is interrupted ? false
    Thread is interrupted ? true

<table> 
 <thead> 
  <tr> 
   <th align="left"><strong><code>可中断方法捕获到了中断信号（signal）之后，也就是捕获了InterruptedException异常之后会擦除掉interrupt的标识</code></strong></th> 
  </tr> 
 </thead> 
</table>

public class ThreadisInterrupted2 {
        
        public static void main(String[] args) throws InterruptedException {
        
            Thread thread = new Thread() {
        
                @Override
                public void run() {
        
                    while (true) {
        
                        try {
        
                            TimeUnit.MINUTES.sleep(1);
                        } catch (InterruptedException e) {
        
                            //ignore the exception
                            //here the interrupt flag will be clear.
                            System.out.printf("I am be interrupted ? %s\n", isInterrupted());
                        }
                    }
                }
            };
    
            thread.setDaemon(true);
            thread.start();
            
            TimeUnit.MILLISECONDS.sleep(2);
            System.out.printf("Thread is interrupted ? %s\n", thread.isInterrupted());
    
            thread.interrupt();
            TimeUnit.MILLISECONDS.sleep(2);
            System.out.printf("Thread is interrupted ? %s\n", thread.isInterrupted());
        }
    }

Thread is interrupted ? false
    I am be interrupted ? false
    Thread is interrupted ? false

<table> 
 <thead> 
  <tr> 
   <th align="left">由于在run方法中使用了sleep这个可中断方法，它会捕获到中断信号，并且会擦除interrupt标识，因此程序的执行结果都会是false</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="left">其实这也不难理解，可中断方法捕获到了中断信号之后，为了不影响线程中其他方法的执行，将线程的interrupt标识复位是一种很合理的设计。</td> 
  </tr> 
 </tbody> 
</table>

<table> 
 <thead> 
  <tr> 
   <th align="left"><code>isInterrupted</code>方法和<code>interrupted</code>方法都调用了同一个本地方法</th> 
   <th align="left"></th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td align="left"><strong>isInterrupted</strong></td> 
   <td align="left"><strong>interrupted</strong></td> 
  </tr> 
  <tr> 
   <td align="left"><code>public boolean isInterrupted() { </code><br><code>return isInterrupted(false);</code><br><code>}</code></td> 
   <td align="left"><code>public static boolean interrupted() { </code><br><code>return currentThread().isInterrupted(true);</code><br><code>}</code></td> 
  </tr> 
 </tbody> 
</table>

\-----------------------------------------------------------------------------读书笔记摘自书名：Java高并发编程详解：多线程与架构设计 作者：汪文君