A sentence out of my anticipation!

Hello Everybody:
Here is a demo to test java's multithread:
class MyThread extends Thread{
    public void run(){
        while(true){
            System.out.println(getName() + " is running!");
            try{
                sleep(1000);
            }catch(InterruptedException e){
                System.out.println(e.getMessage());
                }
            }
        }
    }
class InterruptThreadDemo{
    public static void main(String[] args) throws InterruptedException{
        MyThread m = new MyThread();
        System.out.println("Starting thread...");
        m.start();
        Thread.sleep(2000);
        System.out.println("Interrupt thread...");
        m.interrupt();
        Thread.sleep(2000);
        System.out.println("Stopping application...");
        }
    }

The result is:
Starting thread...
Thread-0 is running!
Thread-0 is running!
Interrupt thread...
Thread-0 is running!
sleep interrupted
Thread-0 is running!
Thread-0 is running!
Stopping application...
Thread-0 is running!
Thread-0 is running!
Thread-0 is running!
Thread-0 is running!
Thread-0 is running!
.......

The outcome is bit out of my anticipation:
What happened to create the sentence "sleep interrupted!"

Any help will be greatly appreciated!