Terminating Thread.Sleep() when another Thread terminates?

Question

I keep getting an interrupt from a thread within a thread and it won't let me destroy the main thread because of it. I would still like to use Thread.sleep() to slow down the loop.

Main Thread:

startEngine.setOnAction((ActionEvent e) -> {

        executor.submit(new Runnable() {
            @Override
            public void run() {
                while (!Thread.currentThread().isInterrupted()) {
                    lifeInstance.runEngine();
                }

            }

        });

    });

stopEngine.setOnAction((ActionEvent e) -> {
        executor.shutdownNow();
    });

executor.submit is calling lifeInstance.runEngine() which is:

public void runEngine() {

    //logic...

    try {
        Thread.sleep(1000);
    } catch (InterruptedException ex) {
        Logger.getLogger(LifeEngine.class.getName()).log(Level.SEVERE, null, ex);

        return;
    }
}

ERRROR:

//Prints out stuff from runEngine()

Nov 06, 2016 6:04:52 PM thecell.LifeEngine runEngine
SEVERE: null
java.lang.InterruptedException: sleep interrupted
    at java.lang.Thread.sleep(Native Method)
    at thecell.LifeEngine.runEngine(LifeEngine.java:66)
    at UIControls.RightControls$1.run(RightControls.java:48)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

//Keeps printing out stuff from runEngine()

Answer 1

Because isInterrupted() returns false , when the runEngine() method returns on the InterruptedException .

From the book "Java Concurrency in Practice":

Blocking library methods like Thread.sleep and Object.wait try to detect when a thread has been interrupted and return early. They respond to interruption by clearing the interrupted status and throwing InterruptedException , indicating that the blocking operation completed early due to interruption.

The interrupted state is cleared when you get the exception. You can reset it before return:

} catch (InterruptedException ex) {
    Logger.getLogger(LifeEngine.class.getName()).log(Level.SEVERE, null, ex);
    Thread.currentThread().interrupt();
    return;
}

Actually, you should do this because your task code is executed by a thread pool, and it's good behaviour to preserve the interrupted state after your task code has processed it. So that the thread pool can respond to the interruption as well.