CODEWITHSUNDEEP
javamultithreading
Jonas Olesen
Jonas Olesen

Reputation: 568

Loop task for given time using Thread.sleep()

I currently have a method i would like to loop for a given time. I have tried creating two threads like this

            Thread t = new Thread();
            t.start();
            Runnable r = new Runnable() {
                @Override
                public void run() {
                    try {
                        Thread.sleep(length);
                        t.interrupt();
                    } catch (InterruptedException ex) {
                    }
                }
            };
            Thread s = new Thread(r);
            s.start();

            while(!t.isInterrupted()){
                runCurrentPres(current);
            }

But I cant seem to break the loop, t is never interrupted for some reason.

Upvotes: 1

Views: 677

Answers (3)

Jonas Olesen
Jonas Olesen

Reputation: 568

Using your suggestions i went with

long end = System.currentTimeMillis() + length;
while(System.currentTimeMillis() < end){
    runCurrentPres(current);
}

as mentioned in comments, the runcurrent takes time to execute because of a for loop. therefor i changed the solution to check before each iteration of the for loop, it ended up like this, and works just as intended

long time = System.currentTimeMillis();
    while (time + length > System.currentTimeMillis()) {
        files = updateFiles(current);
        for (File f : files) {
            if(time + length < System.currentTimeMillis()){
                break;
            }

And yes, the solution with the while(true) inside the thread used 70% cpu

Upvotes: 0

Snild Dolkow
Snild Dolkow

Reputation: 6876

The isInterrupted method is really more of a hasPendingInterruption than wasEverInterrupted. The flag is automatically cleared when an InterruptedException is thrown in that thread (which can only happen at certain points, like when you call sleep), or if anyone calls interrupted() (which is different from isInterrupted()).

Read the official Java tutorial on Interrupts for more info.

Threads that have exited can not have pending interruptions.

However, this is not a good way to limit your main thread's run time. Checking the time in every iteration would achieve what you want:

long end = System.currentTimeMillis() + length;
while(System.currentTimeMillis() < end){
    runCurrentPres(current);
}

Note that this only checks between each runCurrentPres call, so if that function takes a long time to execute, your loop will finish a little later than intended. This is, however, the same behavior that your original code would've had if it worked.

Upvotes: 3

isnot2bad
isnot2bad

Reputation: 24464

So what about this?

long time = System.currentTimeMillis();
while (time + length > System.currentTimeMillis()) {
    runCurrentPres(current);
}

No need to use threads.

Upvotes: 2

Related Questions