Java execute code only after ForkJoinPool submit

I have 1 parallel processing code using ForkJoinPool:

ForkJoinPool customThreadPool = new ForkJoinPool(4);
customThreadPool.submit(() -> {
    list.parallelStream().forEach(this::process);
});

I am invoking this though some controller. This code runs asynchronously so, controller response will be immediate and async process will happen in background.

Now I want to trigger some another processing once above all the process completes. Is there any way or method which executes only after completing ForkJoinPool submit.

I tried submit.isDone and submit.isCompletedNormally but this runs immediate not after completion of submit.

The submit method returns a Future which you need to wait on. So you call get on it. I think some code like this will work in your case

import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;

class Scratch {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        List<String> list = List.of("a", "b", "c");
        ForkJoinPool customThreadPool = new ForkJoinPool(4);
        customThreadPool.submit(() -> {
            list.parallelStream().forEach(Scratch::process);
        }).get();
        customThreadPool.submit(() -> System.out.println("done"));

    }

    private static void process(String s) {
        System.out.println(s);
    }
}

It prints

b
a
c
done

Note the order of a, b, c is not deterministic but done will always be last