线程中断：是否会取消即将到来的wait（）调用？

时间：2011-07-14 19:38:04

标签： java multithreading concurrency wait

我有一个具有传入作业队列的线程（包含作业描述的LinkedList）。当没有工作要做时，线程在队列上阻塞wait()。当外部作业调度程序对象在队列中放置新作业时，会使用notify()唤醒它。

关闭我的程序时，我在线程上调用interrupt()。当线程等待InterruptedException中的作业时，这会引发wait()。我的问题是：如果我在没有阻塞但是做某种工作的情况下中断线程会发生什么，处理后的项目是队列中的最后一个（所以队列现在是空的）并且执行过去isInterrupted()检查之前设置中断标志，以便再次调用wait()？它会抛出一个InterruptedException，因为已经设置了中断标志或者线程永远等待，因为新的作业永远不会到达队列而且没有人可以中断等待吗？

3 个答案:

答案 0 :(得分：11)

阅读Thread.interrupt() -

的API规范
  

中断此主题。

     

除非当前线程正在中断，否则总是如此   允许，调用此线程的checkAccess方法，这可能是   导致抛出SecurityException。

     

如果在调用wait（）时阻塞了这个线程，请等待（long），   或者等待（long，int）Object类或join（）的方法，   join（long），join（long，int），sleep（long）或sleep（long，int）方法   这个类，然后它的中断状态将被清除   收到InterruptedException。

     

如果此线程在可中断的I / O操作中被阻止   然后通道将关闭，线程的中断状态   将被设置，线程将收到ClosedByInterruptException。

     

如果此线程在Selector中被阻塞，那么线程的中断   状态将被设置，它将立即从选择中返回   操作，可能具有非零值，就像选择器一样   唤醒唤醒方法。

     

如果以前的条件都没有，则该线程的中断   状态将被设置。

     

中断非活动的线程无需任何效果。

所以，所有这一切都将是线程的中断状态将被设置。

修改

如果您阅读Object.wait()的API规范，则会看到以下内容 -

  

抛出：

     

InterruptedException - 如果任何线程在当前线程等待a之前或当前线程中断当前线程   通知即可。抛出此异常时，将清除当前线程的中断状态。

答案 1 :(得分：9)

是的，你的被中断的线程在调用wait（）时会抛出InterruptedException。这对你自己来说非常简单。

public class TestInt {
    public static void main(String[] args) throws Exception
    {
        Thread.currentThread().interrupt();

        synchronized(TestInt.class) {
            TestInt.class.wait();
        }    
    }    
}

另外，请注意Object.wait()的javaodc：

  

InterruptedException - 如果任何线程在之前或之后中断当前线程   当前线程正在等待通知。当前中断状态   抛出此异常时清除线程。

答案 2 :(得分：1)

虽然这是一个很老的问题，但我想补充一点，如果您在 Thread.currentThread().interrupt() 期间调用 lock.wait() 方法（而线程处于 WAITING 状态），它不会意味着线程将在内部立即抛出 InterruptedException，第一个线程将进入 BLOCKED 状态（它被唤醒，就像来自另一个线程的 lock.notify()/notifyAll() 调用一样，这允许它竞争共享锁) 将中断标志设置为 true，可能在一段时间后仅在再次获取锁定后（有时相当长的时间）它可以抛出一个 InterruptedException（没有锁定它无法继续，甚至处理异常）。

package com.company;

public class Main {

    public static void main(String[] args) {
        final Object lock = Main.class;

        // three simple threads
        Thread th1 = new Thread(() -> {
            synchronized (lock) {
                for (int i = 0; i < 15; i++) {
                    sleepWithoutException(100);
                    System.out.println("th1 is doing some job!");
                }
            }
        });

        Thread th2 = new Thread(() -> {
            synchronized (lock) {
                for (int i = 0; i < 15; i++) {
                    sleepWithoutException(100);
                    System.out.println("th2 is doing some job!");
                }
            }
        });

        Thread th3 = new Thread(() -> {
            synchronized (lock) {
                for (int i = 0; i < 15; i++) {
                    sleepWithoutException(100);
                    System.out.println("th3 is doing some job!");
                }
            }
        });

        // thread which will be in WAITING state after 1 second
        Thread th4 = new Thread(() -> {
            synchronized (lock) {
                try {
                    sleepWithoutException(500);
                    lock.wait();
                    System.out.println("Continued");
                } catch (InterruptedException e) {
                    System.out.println("interrupted! " + e);
                    System.exit(1);
                }
            }
        });


        // execution
        th4.start();

        sleepWithoutException(100);

        th1.start();
        th2.start();
        th3.start();

        // thread which will monitor states of other threads
        new Thread(() -> {
            long start = System.currentTimeMillis();
            for (int i = 0; i < 1000_000; i++) {
                sleepWithoutException(100);
                System.out.println("-------------------------------------------------");
                System.out.println("step: " + i + " , timeElapsed: " + (System.currentTimeMillis() - start));
                if (i == 10) {
                    th4.interrupt();
                }
                System.out.println(
                        th1.getState() + " " + th1.isInterrupted() + "\n" +
                                th2.getState() + " " + th2.isInterrupted() + "\n" +
                                th3.getState() + " " + th3.isInterrupted() + "\n" +
                                th4.getState() + " " + th4.isInterrupted()
                );
            }
        }).start();


    }

    public static void sleepWithoutException(long time) {
        try {
            Thread.sleep(time);
        } catch (InterruptedException e) {
            System.out.println("fallen in sleep" + e);
        }
    }
}

请参阅下面的日志，因为您可以看到其他线程在 BLOCKING 状态且标志 isInterrupted 的 th4 设置为 true 时继续工作（在调用 Thread.currentThread().interrupt() 方法之后） 

-------------------------------------------------
step: 0 , timeElapsed: 101
BLOCKED false
BLOCKED false
BLOCKED false
TIMED_WAITING false
-------------------------------------------------
step: 1 , timeElapsed: 201
BLOCKED false
BLOCKED false
BLOCKED false
TIMED_WAITING false
-------------------------------------------------
step: 2 , timeElapsed: 301
BLOCKED false
BLOCKED false
BLOCKED false
TIMED_WAITING false
-------------------------------------------------
step: 3 , timeElapsed: 401
BLOCKED false
BLOCKED false
TIMED_WAITING false
WAITING false
th3 is doing some job!
-------------------------------------------------
step: 4 , timeElapsed: 502
BLOCKED false
BLOCKED false
TIMED_WAITING false
WAITING false
th3 is doing some job!
-------------------------------------------------
step: 5 , timeElapsed: 602
BLOCKED false
BLOCKED false
TIMED_WAITING false
WAITING false
th3 is doing some job!
-------------------------------------------------
step: 6 , timeElapsed: 703
BLOCKED false
BLOCKED false
TIMED_WAITING false
WAITING false
th3 is doing some job!
-------------------------------------------------
step: 7 , timeElapsed: 803
BLOCKED false
BLOCKED false
TIMED_WAITING false
WAITING false
th3 is doing some job!
-------------------------------------------------
step: 8 , timeElapsed: 904
BLOCKED false
BLOCKED false
TIMED_WAITING false
WAITING false
th3 is doing some job!
-------------------------------------------------
step: 9 , timeElapsed: 1004
BLOCKED false
BLOCKED false
TIMED_WAITING false
WAITING false
th3 is doing some job!
-------------------------------------------------
step: 10 , timeElapsed: 1105
BLOCKED false
BLOCKED false
TIMED_WAITING false
WAITING true
th3 is doing some job!
-------------------------------------------------
step: 11 , timeElapsed: 1205
BLOCKED false
BLOCKED false
TIMED_WAITING false
BLOCKED true
th3 is doing some job!
-------------------------------------------------
step: 12 , timeElapsed: 1306
BLOCKED false
BLOCKED false
TIMED_WAITING false
BLOCKED true
th3 is doing some job!
-------------------------------------------------
step: 13 , timeElapsed: 1406
BLOCKED false
BLOCKED false
TIMED_WAITING false
BLOCKED true
th3 is doing some job!
-------------------------------------------------
step: 14 , timeElapsed: 1507
BLOCKED false
BLOCKED false
TIMED_WAITING false
BLOCKED true
th3 is doing some job!
-------------------------------------------------
step: 15 , timeElapsed: 1607
BLOCKED false
BLOCKED false
TIMED_WAITING false
BLOCKED true
th3 is doing some job!
-------------------------------------------------
step: 16 , timeElapsed: 1708
BLOCKED false
BLOCKED false
TIMED_WAITING false
BLOCKED true
th3 is doing some job!
-------------------------------------------------
step: 17 , timeElapsed: 1808
BLOCKED false
BLOCKED false
TIMED_WAITING false
BLOCKED true
th3 is doing some job!
-------------------------------------------------
step: 18 , timeElapsed: 1909
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 19 , timeElapsed: 2009
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 20 , timeElapsed: 2110
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 21 , timeElapsed: 2211
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 22 , timeElapsed: 2311
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 23 , timeElapsed: 2412
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 24 , timeElapsed: 2512
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 25 , timeElapsed: 2613
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 26 , timeElapsed: 2713
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 27 , timeElapsed: 2814
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 28 , timeElapsed: 2914
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 29 , timeElapsed: 3015
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 30 , timeElapsed: 3115
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 31 , timeElapsed: 3216
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 32 , timeElapsed: 3316
BLOCKED false
TIMED_WAITING false
TERMINATED false
BLOCKED true
th2 is doing some job!
-------------------------------------------------
step: 33 , timeElapsed: 3417
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 34 , timeElapsed: 3517
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 35 , timeElapsed: 3618
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 36 , timeElapsed: 3718
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 37 , timeElapsed: 3819
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 38 , timeElapsed: 3919
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 39 , timeElapsed: 4019
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 40 , timeElapsed: 4120
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 41 , timeElapsed: 4220
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 42 , timeElapsed: 4321
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 43 , timeElapsed: 4421
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 44 , timeElapsed: 4522
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 45 , timeElapsed: 4622
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 46 , timeElapsed: 4723
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
-------------------------------------------------
step: 47 , timeElapsed: 4823
TIMED_WAITING false
TERMINATED false
TERMINATED false
BLOCKED true
th1 is doing some job!
interrupted! java.lang.InterruptedException

Process finished with exit code 1
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