一旦线程被中断，如何完全停止线程？

Question

In my current code I am creating a thread that implements runnable . I am starting it in the main then letting the main interrupt it. However it once it is interrupted it continues to run. I would like the thread to completely stop.

Thread Class:

public class MyThread implements Runnable {

    @Override
    public void run() {

        // string relating to the threads name
        // Note that you actually set the threads name in the main
        String threadName = Thread.currentThread().getName();


        System.out.println(threadName + " is now started...");

        System.out.println(threadName + " about to count down...");

        for (int loop = 100; loop > 1; loop--) {

            try {           
                //for 0.5 seconds
                Thread.sleep(500);      
            } catch (InterruptedException e) {
                e.printStackTrace();
                System.out.println(threadName + " was Interupted!");        
            }               

            System.out.println(loop);
        }           

    }

}

Main:

public class Runner {

    public static void main(String[] args) {

        //Create thread from class
        MyThread myt= new MyThread();

        //Passing in the thread from class and also naming it
        Thread t= new Thread(myt, "My Thread");

        //Actually starts the thread
        t.start();

        //Main thread has a sleep for 5 seconds then interrupts t
        try {
            Thread.sleep(5000);
            t.interrupt();
            System.out.println("Interupting...");
        } catch (InterruptedException e) {
            e.printStackTrace();                
        }       

    }

}

Output (note how thread does not stop):

My Thread is now started...
My Thread about to count down...
100
99
98
97
96
95
94
93
92
Interupting...
java.lang.InterruptedException: sleep interrupted
My Thread was Interupted!
91
    at java.lang.Thread.sleep(Native Method)
    at threads.MyThread.run(MyThread.java:22)
    at java.lang.Thread.run(Unknown Source)
90
89
88
87
86
85

Answer 1

Just break out of the loop:

catch (InterruptedException e) {
    e.printStackTrace();
    System.out.println(threadName + " was Interupted!");
    Thread.currrentThread().interrupt();
    break;
}

Answer 2

Simply use a boolean flag that will be checked before doing any operation in the run() method and based on its state do whatever is needed. Make sure it should be volatile .

simply call myt.setRunning(false) instead of t.interrupt()

Sample cde:

class MyThread implements Runnable {

    private volatile boolean isRunning=true;

    @Override
    public void run() {             

        for (int loop = 100; loop > 1; loop--) {                 

            if(!isRunning){
               // break or do whatever is needed here
            }             
        }    
    }               

}

Answer 3

Just write the run() method correctly, so that it breaks out of the loop when interrupted, rather than just continuing.

Thread does have a stop() method , but it's deprecated for a reason; it can leave things in an inconsistent and potentially unstable state. Don't use it!

Answer 4

For such a repeating task you could also use a TimerTask :

Just note this code won't stop at zero.

public class CountdownTask extends TimerTask {

    private int from;

    public CountdownTask(int from) {
        this.from = from;
    }

    @Override
    public void run() {
        System.out.println(from--);
    }
}

private void example() throws InterruptedException {
    Timer timer = new Timer("Countdown");
    timer.schedule(new CountdownTask(100), 0, 500);
    Thread.sleep(2000); //do something
    timer.cancel(); //stop task
}