CODEWITHSUNDEEP
javamultithreadinginterrupt
user3287264
user3287264

Reputation:

How to completely stop a thread once it has been interrupted?

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

Upvotes: 0

Views: 189

Answers (4)

Octavia Togami
Octavia Togami

Reputation: 4306

Just break out of the loop:

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

Upvotes: 3

Braj
Braj

Reputation: 46841

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
            }             
        }    
    }               

}

Upvotes: 2

weston
weston

Reputation: 54791

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
}

Upvotes: 0

Ernest Friedman-Hill
Ernest Friedman-Hill

Reputation: 81694

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!

Upvotes: 0

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