submit method won't invoke onNext FLOW STREAM API JAVA

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I'm learning about the FLOW Stream API in Java and I'm currently creating an example based on the one that is on oracle community. The problem is that I don't get to see the expected output but just the SUBSCRIBING string that is printed inside onSubscribe method. I already checked and found submissionpublisher-on-submit-not-invoking-onnext-of-subscriber on StackOverflow, but didn't work because I was already calling request(Long N). 

import java.util.concurrent.Flow;

public class Computer<T> implements Flow.Subscriber<T> {

    private Flow.Subscription subscription;

    @Override
    public void onSubscribe(Flow.Subscription subscription) {
        this.subscription = subscription;
        System.out.println("SUBSCRIBING");
        this.subscription.request(1);
    }

    @Override
    public void onNext(T item) {
        System.out.println(String.format("Got %s", item.toString()));
        this.subscription.request(1);
    }

    @Override
    public void onError(Throwable throwable) {
        throwable.printStackTrace();
    }

    @Override
    public void onComplete() {
        System.out.println("DONE");
    }

}

--

import java.util.List;
import java.util.concurrent.SubmissionPublisher;

public class Sensor {

    public static void main(String[] args) {
        SubmissionPublisher<String> submissionPublisher = new SubmissionPublisher<>();
        Computer<String> subscriber = new Computer<>();
        submissionPublisher.subscribe(subscriber);

        List<String> items = List.of("1.25", "1.224", "1.55");
        items.forEach(submissionPublisher::submit);
        submissionPublisher.close();
    }

}

And I just get to see:

SUBSCRIBING

Why onNext method is not being called?

java-9 publish-subscribe reactive-programming java
1 Answers

You are not passing a ScheduledExecutorService to the Publisher which is basically an ExecutorService which can schedule tasks to run after a delay or to execute repeatedly with a fixed interval of time in between each execution.

import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.SubmissionPublisher;

public class Sensor {

    public static void main(String[] args) {
        ScheduledExecutorService executor = Executors.newScheduledThreadPool(Runtime.getRuntime().availableProcessors());
        SubmissionPublisher<String> submissionPublisher = new SubmissionPublisher<>(executor, 5);
        Computer<String> subscriber = new Computer<>();
        submissionPublisher.subscribe(subscriber);

        List<String> items = List.of("1.25", "1.224", "1.55");
        items.forEach(submissionPublisher::submit);
        submissionPublisher.close();
        executor.shutdown();
    }
}
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