java Thread#isInterrupt 对于死线程总是返回 false

Question

这个问题已经有答案了:

Why does Thread.isInterrupted () always return false? (4 个回答)

已关闭 5 年前。

我遇到了奇怪的行为。所有消息来源都表明，在捕获中断异常后，您需要调用 Thread.currentThread().interrupt() 来恢复中断标志。但我尝试创建简单的应用程序，在进程中断后检查中断状态

public class Main {
    public static void main(String[] args) throws InterruptedException {
        Runnable r = () -> {
            try {
                Thread.sleep(100000);
            } catch (InterruptedException e) {
                System.out.println("interrupted exception is occurred");
                Thread.currentThread().interrupt();
                System.out.println("interrupt flag is updated:" + Thread.currentThread().isInterrupted());
            }
        };

        Thread thread = new Thread(r);
        thread.start();
        thread.interrupt();

        boolean interruptFlag;
        do {
            Thread.sleep(1000);
            interruptFlag = thread.isInterrupted();
            System.out.println("interrupt flag:" + interruptFlag + " isAlive:" + thread.isAlive());
        } while (!interruptFlag);
    }
}

如果你尝试运行它，那么你会得到

interrupted exception is occurred
interrupt flag is updated:true
interrupt flag:false isAlive:false
interrupt flag:false isAlive:false
interrupt flag:false isAlive:false
interrupt flag:false isAlive:false
interrupt flag:false isAlive:false

它将无限地工作。问题是为什么线程死后，iterrupt flag 为 false？

Answer 1

当您从主线程检查中断状态时，第二个线程已经死亡，因此它返回 false。尝试将 Thread.sleep(1000) 放在等待循环的末尾，您将在中断状态中看到 true。

此行为没有记录，因此很难说它是缺乏文档还是现有实现的功能。私有(private)原生 boolean isInterrupted(boolean ClearInterrupted) 的实现；方法需要检查才能说得更多。

类似讨论:Thread.isInterrupted() returns false after thread has been terminated