Java Executor Service Is Not Processing Parallely

Question

I am attempting to run multiple services parallely using ExecutorService. But i failed to execute parallely.

I have written java.util.concurrent.TimeUnit.MINUTES.sleep(1) to wait one minute in Service1 class.

But Service2 is processing only after Service1 processed.

Below is my code snippet, Kindly correct me/code if my understand about ExecutorService is wrong

public void startService() {

    try {
        ExecutorService service = Executors.newFixedThreadPool(3);
        service.submit(new Service1());
        service.submit(new Service2());
        service.submit(new Service3());

        service.shutdown();
        service.awaitTermination(1, TimeUnit.MINUTES);

        System.exit(0);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

public class Service1 implements Callable<Object> {

    {
        try {
            java.util.concurrent.TimeUnit.MINUTES.sleep(1);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public Object call() throws Exception {
        return null;
    }
}

public class Service2 implements Callable<Object> {

    @Override
    public Object call() throws Exception {
        System.out.println(" Service 2 "); // It prints after 1 minute only.
        return null;
    }
}

public class Service3 implements Callable<Object> {

    @Override
    public Object call() throws Exception {
        System.out.println(" Service 3 "); 
        return null;
    }
}

more precisely, Service1 starts before Service2, but ends after — Maurice Perry, Feb 20 '17 at 13:18
@Siva "when i put as global sop { }" -- I'm not sure what you mean with "global sop {} ", but why don't you test that the code that you post reproduces the problem? That saves everyone a lot of time. And make sure that it compiles. — Erwin Bolwidt, Feb 20 '17 at 13:28
@Siva move your code from initialization block to call method in Service1 — rvit34, Feb 20 '17 at 13:33
Better suggestion that explains what you are doing in the {} block: [What is an initialization block?](http://stackoverflow.com/questions/3987428/what-is-an-initialization-block) — Erwin Bolwidt, Feb 20 '17 at 13:33

Maurice Perry · Accepted Answer · 2017-02-20T13:41:28.223

2

The code:

{
    try {
        java.util.concurrent.TimeUnit.MINUTES.sleep(1);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

is a constructor, and it is called by the main thread when it's doing new Service1(). So yeah, it must complete before it has a chance to submit the services.

UPDATE:

In your original post, the sleep was in the call method, and it worked. Now, your Service1 is equivalent to:

public class Service1 implements Callable<Object> {

    public Service1() {
        try {
            java.util.concurrent.TimeUnit.MINUTES.sleep(1);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public Object call() throws Exception {
        return null;
    }
}

And only the call method is run by the executor. the Service1 instance cannot even be submitted before the constructor completes.

edited Feb 20 '17 at 13:41

answered Feb 20 '17 at 13:30

Maurice Perry

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Sorry Maurice. I am new thread, can you please elaborateif you dont mind. – deadend Feb 20 '17 at 13:33
You are saying that Service2 will invoke only after Service1 initialization completes right? – deadend Feb 20 '17 at 13:37
@ Maurice Perry. I understood it. Thank you very much. – deadend Feb 20 '17 at 13:40

Java Executor Service Is Not Processing Parallely

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