JAVA real time consol-control the threads

Question

I am a beginner in programming. I am still learning about threads and more of them. But now I have quite a big idea to write my first program (I mean bigger than simple calculator). I want it to sort files, integrate in one (many copies of one file in different localization - the idea of it is of no importance now).

But I want to create threads, or anything else (what is your advice). I mean. When I start the program, the console starts up, and e.g I have to write "my_programm run" or "my_program stop" or "my_program status" or "my_magic_tricks be_done". I mean how can i create a program working in the background like in threads with real time string control over it. I tried to find out on Google for anything which could be useful for me, but i didn't find it out.

Please give me just a name of libraries or methods, which I can use. I will read out, what it is about and finally I will move forward with it.

If it is a dumbass question. I am really sorry for disapointing the programmer group. But it would be nice to be given of any signpost or clue.

Welcome to Stack Overflow. I know, it can be overwhelming. Can you break this question into smaller questions that are more _directly_ answerable? Be as clear and simple as possible. Here, it appears that you want to do too many things at once. — Kedar Mhaswade, Apr 21 '16 at 21:59
Maybe you are right. What libraries should I use, which make real-time reading the command line. — xross, Apr 21 '16 at 22:04
If you're a beginner, stay away from threads for now. There are a lot of more basic things to learn first that will stand you in better stead. — Andy Turner, Apr 21 '16 at 22:05
I want my program to run in the background. It is possible, that it will be working for many hours. So, for example during that process I want it to shut down safely (I will write it manually, how he should exit). But how can I give him a singnal for stopping the thread in my safe-mode — xross, Apr 21 '16 at 22:05

Dici · Accepted Answer · 2016-04-21T22:22:51.903

A simple way to do it using the standard library :

import java.util.Scanner;
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.ThreadPoolExecutor;

import static java.util.concurrent.TimeUnit.MILLISECONDS;

public class Example {
    private static final int POOL_SIZE = 5;
    private static final ExecutorService WORKERS = new ThreadPoolExecutor(POOL_SIZE, POOL_SIZE, 1, MILLISECONDS, new LinkedBlockingDeque<>());

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (true) {
            System.out.print("> ");
            String cmd = sc.nextLine();
            switch (cmd) {
                case "process":
                    WORKERS.submit(newExpensiveTask());
                    break;

                case "kill":
                    System.exit(0);

                default:
                    System.err.println("Unrecognized command: " + cmd);
            }
        }
    }

    private static Runnable newExpensiveTask() {
        return () -> {
            try {
                Thread.sleep(10000);
                System.out.println("Done processing");
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
        };
    }
}

This code lets you run heavy tasks asynchronously while the user terminal remains available and reactive.

Whoa, didnt know it could be made in such an easy way. Thank you for this ;). I am sure I will use it in my idea. — xross, Apr 21 '16 at 22:15
@xross no problem. If it helps, I'll be happy to get an upvote :D — Dici, Apr 21 '16 at 22:19
I did it, but the upvote will be marked just after I will gain more reputation points :/. So be patient it will be voted ;). Thank you — xross, Apr 21 '16 at 22:24

score 0 · Answer 2 · answered Apr 21 '16 at 22:07

I would recommend reading up on specific tutorials, such as the Java Language Tutorial (available as a book - at least, it used to be - as well as on the Java website https://docs.oracle.com/javase/tutorial/essential/concurrency/)

However as others have cautioned, getting into threading is a challenge and requires good knowledge of the language quite apart from the aspects of multithreading and synchronization. I'd be tempted to recommend you read some of the other tutorials - working through IO and so on - first of all.

In my opinion, I am able to do a good IO. I have made something like celluar automaton, which simulates cell live :). It wasn't so hard, I think so. Maybe it isnt so advanced but it was a good exercise — xross, Apr 21 '16 at 22:11

JAVA real time consol-control the threads

2 Answers2