java中线程的中断状态标志在哪里，为什么interrupted（）方法是静态的

Question

First question is : where is the interrupted status flag that interrupt() method supposedly sets :

 public void interrupt() {
            if (this != Thread.currentThread())
                checkAccess();

            synchronized (blockerLock) {
                Interruptible b = blocker;
                if (b != null) {
                    interrupt0();           // Just to set the interrupt flag
                    b.interrupt(this);
                    return;
                }
            }
            interrupt0();
        }

Second question is : why is interrupted() method is static ? and isInterrupted not static ?

Answer 1

The language specification doesn't dictate how the interruption status should be implemented. In hotspot, you can find the implementation details in the JVM code. For example, for linux, it's here around line 4140.

interrupted is static because it checks the current thread status. In other words, if you call new Thread().interrupted() on the main thread, you will get true if the main thread is interrupted, not if the new Thread is interrupted.

isInterrupted checks whether the thread on which you call the method is interrupted. In the example above, it would return the status of new Thread() , ie false.

Finally, an important difference between the two methods is that interrupted clears the interruption status. It is generally good practice to reset it, unless your code is responsible for the lifecycle of the given thread:

if (Thread.interrupted()) {
  Thread.currentThread().interrupt();
  //etc.
}