java - 是否中断 sleep 线程释放对象上的锁的异常

Question

当线程处于 sleep 状态时，它仍然持有对象的锁，当它被中断时，它会释放锁并进入就绪状态，还是会继续执行而不改变状态？

Answer 1

When it is interrupted, does it release the lock and go to ready state or will it continue the execution without changing the state?

线程被中断只是状态改变(已设置的标志)而不是状态改变，对是否释放锁没有影响。

持有对象监视器的线程只有在相应对象实例上调用wait(有或没有超时)时才会释放它，或者当它从同步块(synchronized block)中退出时，无论是否被中断，都不会释放它。不要更改此规则的任何内容。

---

这是一个简单的代码，展示了这个想法:

// Used to make sure that thread t holds the lock before t2
CountDownLatch latch = new CountDownLatch(1);
Thread t = new Thread(
    () -> {
        synchronized (someObject) {
            // Release t2
            latch.countDown();
            for (int i = 1; i <= 2; i++) {
                try {
                    System.out.println("Sleeping " + i);
                    // Sleep 2 sec and keep holding the lock
                    Thread.sleep(2_000L);
                    System.out.println("Sleep over " + i);
                } catch (InterruptedException e) {
                    System.out.println("Interrupted " + i);
                }
            }
        }
    }
);
Thread t2 = new Thread(
    () -> {
        try {
            // Wait to be release by t
            latch.await();
        } catch (InterruptedException e) {
            throw new IllegalStateException(e);
        }
        System.out.println("Trying to get in");
        synchronized (someObject) {
            System.out.println("In");
        }
    }
);
// Start the threads
t.start();
t2.start();
// Waiting 1 sec (< 2 sec) only before interrupting t
Thread.sleep(1_000L);
// Interrupt t
t.interrupt();

输出:

Trying to get in
Sleeping 1
Interrupted 1
Sleeping 2
Sleep over 2
In

正如您在输出中看到的那样，只有当线程 t 从同步块(synchronized block)退出时，线程 t2 才会进入同步块(synchronized block)(获取锁)。线程t被中断的事实并没有使它释放锁。