How to exit 2D game simulation (only) without exiting the Java code?

Question

I (new to Java) am working on a decades old Java project built using Golden T Studios Game dev jdk. I have a game in the project which runs a 2D simulation. The code structure in a nutshell is as follows:

package game;
import java.io.*;
import java.lang.reflect.Field;
import javax.swing.JFrame;

import com.golden.gamedev.GameLoader;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import sometcpimports.*;

public class MainGAME extends JFrame implements Runnable {

    public static void main(String[] args) { //call new MainGAME;
    }

    public MainGAME() {//initiate game parameters; 
    //start new THREAD; 
    }

   @Override
   public void run() { //initiate new game and environment;
    game = new GameLoader();
    gameenv = new GameEnvironment(params); //This class is in another file "public class GameEnvironment extends Game {}" 
    //I don't clearly undertsand what the following lines do, so I'm mentioning them as is;

    game.setup(gameenv, dimensions);
    this.setVisible(false);
    gameenv.setVisible(false);
    game.start();
    game.setVisible(true);

    //tbd (code reaches this step)

    }
}

My goal is to run the above simulation multiple times (with different inputs each time) and extract information after each run in a new main class as follows.

public class gamedriver {
    public static void main(String[] args) {
        MainGAME.params = some params;
        MainGAME.main(); // runs the simulation;

        //tbd1 (code doesn't reach this step)
    }
}

The issue is that, on running the simulation from a different file (new main class), I am unable to exit 2D simulator after one run. The code doesn't reach //tbd1 in the new main class which has some output print statements. Essentially I want to simply exit simulator and not the whole JVM. So far I've tried:

1. game.stop() & gameenv.finish() at //tbd which does nothing.
2. System.exit(0) at //tbd which exits game after simulation but also exits jvm and doesnt reach the other main class.
3. finish() at both //tbd and GameEnvironment class which behaves exactly like point 2.

Additionally, I am unable to run the above (MainGAME in gamedriver class) in a for loop. This throws Game.Exception error . I understand it has something to do with threads but I'm not sure how to run them.

Thank you for your time. Appreciate your help!

Answer 1

I found a method to solve the above problem. I'm posting my workaround as a reference for someone who encounters a similar issue. Please note that there might be other (better) solutions out there.

1. I disabled all (any) threads implementation in the MainGAME (by simply commenting it out).
2. I added System.out.println() in MainGAME to print all my outputs at the end of simulation.
3. My second script uses Runtime processes to execute MainGAME:

public class gamedriver {
    public static void main(String[] args) {
        try {
            String separator = System.getProperty("file.separator");
            String classpath = System.getProperty("java.class.path");
            String path = System.getProperty("java.home") + separator + "bin" + separator + "java";
            String[] command = new String[]{path, "-cp", classpath, gamedriver.GAME.class.getName(), "output.csv"};
            Process process = Runtime.getRuntime().exec(command);
            process.waitFor();
        } catch (IOException | InterruptedException e) {
            e.printStackTrace();
        }
    }

    static class GAME {

        public static void main(String args[]) {
            PrintStream out = null;
            try {
                out = new PrintStream(args[1]); 
            } catch (FileNotFoundException p) {
                p.printStackTrace();
            }

            System.setOut(out);// this catches all output from the game to a csv file (output.csv)
            MainGAME temp = new MainGame(some params); // initiate the simulation
            temp.run()
            out.close();
            System.exit(0); // force close the simulator
        }
    }
}

4. I parse output.csv to get the solution.

This might be a sloppy way to solve the issue, but it worked for me, especially because none of the other methods provided by GTGE worked.