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> 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 the 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
* status 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()) {
break;
}
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(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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