Communication between processes (main) Java

Question

I need to communicating various processes as it follows:

First I invoke GeneralMain with args[0] = 1, so it will call A.main().

The two remaining processes will launch in a space of random time, but both processes need to start at the same time.

My code:

public class GeneralMain {

    public static void main(String[] args) {
        int num_proc = Integer.parseInt(args[0]);

        switch (num_proc) {
            case 1:
                A.main(...);
                break;

        case 2:
            B.main(...);
            break;

            case 3:
                C.main(...);
                break;

            default:
                break;
        }
    }
}

First the GeneralMain recieve args[0] = 1, and calls A.main(); .

So, I execute the GeneralMain for three times. In the first time A.main() is started and is the responsible of recieve messages, Then I execute GeneralMain that start B.main() process and send the first message to A. To end, I execute GeneralMain that start C.main() process and send the second message to A, but I need that B.main() and C.main() starts at the same time and send his message at the same time

Thanks.

Answer 1

You might look at using threads and runnable's.

From main you could start A then start 2 threads using a random time at which they would both start. One thread calls B and the other calls C.

Answer 2

You can use a cyclic barrier to make sure B and C start executing their logic at the same time.

CyclicBarrier cyclicBarrier = new CyclicBarrier(2); //global scope

B { //thread B's main
    cyclicBarrier.await(); //wait for other thread
}
C { //thread C's main
    cyclicBarrier.await(); //wait for other thread
}

Basically both B and C will register themselves at the barrier and as soon as the registered parties number reaches 2 the barrier will trip and B and C will start executing their logic at more or less the same time (not sure how exact the synchronization is)