InterruptedException：设置中断标志时是否需要 Thread.currentThread().interrupt()

Question

We all know that when catching an interruptedexception we are supposed to Thread.currentThread().interrupt();

However, from my tests, that flag is already set.

        Thread t = new Thread(() -> {
           try {
              Thread.sleep(1000L);
           } catch (InterruptedException e) {
              // Thread.currentThread().interrupt();
           }
        });
        t.start();
        System.out.println(t.isInterrupted());
        t.interrupt();
        System.out.println(t.isInterrupted());

Prints:

false
true

So what is the point of that commented out line?

Answer 1

If the line is commented out and you try to check in the thread itself if it is interrupted, you will get false as response.

Thread t = new Thread(() -> {
    try {
        Thread.sleep(1000L);
     } catch (InterruptedException e) {
         // Thread.currentThread().interrupt();
     }
     System.out.println(Thread.currentThread().isInterrupted());//false
 });

If you execute the line you get true.

Thread t = new Thread(() -> {
    try {
        Thread.sleep(1000L);
     } catch (InterruptedException e) {
         Thread.currentThread().interrupt();
     }
     System.out.println(Thread.currentThread().isInterrupted());//true
 });