Java线程中的interrupt方法解读

interrupt方法

首先梳理Thread关于interrupt的定义

/**
 * Interrupts this thread.
 *
 * <p> Unless the current thread is interrupting itself, which is
 * always permitted, the {@link #checkAccess() checkAccess} method
 * of this thread is invoked, which may cause a {@link
 * SecurityException} to be thrown.
 *
 * <p> If this thread is blocked in an invocation of the {@link
 * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
 * Object#wait(long, int) wait(long, int)} methods of the {@link Object}
 * class, or of the {@link #join()}, {@link #join(long)}, {@link
 * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)},
 * methods of this class, then its interrupt status will be cleared and it
 * will receive an {@link InterruptedException}.
 *
 * <p&gjst; If this thread is blocked in an I/O operation upon an {@link
 * Java.nio.channels.InterruptibleChannel InterruptibleChannel}
 * then the channel will be closed, the thread's interrupt
 * status will be set, and http://www.devze.comthe thread will receive a {@link
 * java.nio.channels.ClosedByInterruptException}.
 *
 * <p> If this thread is blocked in a {@link java.nio.channels.Selector}
 * then the thread's interrupt status will be set and it will return
 * immediately from the selection operation, possibly with a non-zero
 * value, just as if the selector's {@link
 * java.nio.channels.Selector#wakeup wakeup} method were invoked.
 *
 * <p> If none of the previous conditions hold then this thread's interrupt
 * staDmxooxtus will be set. </p>
 *
 * <p> Interrupting a thread that is not alive need not have any effect.
 *
 * @throws  SecurityException
 *          if the current thread cannot modify this thread
 *
 * @revised 6.0
 * @spec jsR-51
 */
public void interrupt() 

这里讲述了Thread实例对象调用方法interrupt,有这几种情况

? 1.在线程里面有wait,sleep,join方法,会弹出InterruptedException,状态会被清除

? 2.io里面,会弹出异常,状态会被设置,…

? 3.如果线程阻塞在nio中的Selector中,状态会被设置,…

? 4.如果不是上面,这些情况,状态会被设置

可以看出interrupt是关于状态的设置

我们来验证一下

第一种,没有任何情况的

public static void main(String[] args) {
    Thread t1 = new Thread(()->{
       while(true){
           if (interrupted()) {
               brjavascripteak;
           }
           System.out.println("i" + new Date());
       }
    });
    t1.start();
    try {
        Thread.sleep(1000);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    t1.interrupt();
}

线程会在(1000+)ms后结束,整个程序也会结束

第二种,有sleep的情况下

public static void main(String[] args) {
    Thread t1 = new Thread(()->{
       while(true){
           if (interrupted()) {
               break;
           }
           try {
               Thread.sleep(100);
           } catch (InterruptedException e) {
               e.printStackTrace();
           }

           System.out.println("i" + new Date());
       }
    });
    t1.start();
    try {
        Thread.sleep编程客栈(1000);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    t1.interrupt();
}

方法并不会退出,只是打出了一个InterruptException

如何处理中断？

• 上文都在介绍如何获取中断状态，那么当我们捕获到中断状态后，究竟如何处理呢？
• Java类库中提供的一些可能会发生阻塞的方法都会抛InterruptedException异常，如：BlockingQueue#put、BlockingQueue#take、Object#wait、Thread#sleep。
• 当你在某一条线程中调用这些方法时，这个方法可能会被阻塞很长时间，你可以在别的线程中调用当前线程对象的interrupt方法触发这些函数抛出InterruptedException异常。
• 当一个函数抛出InterruptedException异常时，表示这个方法阻塞的时间太久了，别人不想等它执行结束了。
• 当你的捕获到一个InterruptedException异常后，亦可以处理它，或者向上抛出。
• 抛出时要注意？？？：当你捕获到InterruptedException异常后，当前线程的中断状态已经被修改为false(表示线程未被中断)；此时你若能够处理中断，则不用理会该值；但如果你继续向上抛InterruptedException异常，你需要再次调用interrupt方法，将当前线程的中断状态设为true。
• 注意：绝对不能“吞掉中断”！即捕获了InterruptedException而不作任何处理。这样违背了中断机制的规则，别人想让你线程中断，然而你自己不处理，也不将中断请求告诉调用者，调用者一直以为没有中断请求。

更新相关interrupt方法的意义

public void interrupt()

Thread里面的打断函数,可以使用新建一个Thread对象,执行thread.interrupt();

修改调用线程的interrupt 的status

public static boolean interrupted()

该方法可以判断是否被打断,但是这个interrupt的status会被清除,

/**
     * Tests whether the current thread has been interrupted.  The
     * <i>interrupted status</i> of the thread is cleared by this method.  In
     * other words, if this method were to be called twice in succession, the
     * second call would return false (unless the current thread were
     * interrupted again, after the first call had cleared its interrupted
     * status and before the second call had examined it).
     *
     * <p>A thread interruption ignored because a thread was not alive
     * at the time of the interrupt will be reflected by this method
     * returning false.
     *
     * @return  <code>true</code> if the current thread has been interrupted;
     *          <code>false</code> otherwise.
     * @see #isInterrupted()
     * @revised 6.0
     */

public boolean isInterrupted()

该方法可以判断是否被打断

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