How to launch an independent java class from another class?

Question

I need a "main" class that creates other independent class instances. They are independent in that they have their own console and if i close 1 the others don't close.

example: i have these 2 classes

public class Class1 {

    public static void main(String[] args) {
        new Class1();
    }

    Class1() {
        System.out.println("class1");
        Scanner sc = new Scanner(System.in);
        sc.next(); // just to stop runtime from exiting. it suspends it
    }
}

and

public class Class2 {

    public static void main(String[] args) {
        new Class2();
    }

    Class2() {
        System.out.println("class2");
        Scanner sc = new Scanner(System.in);
        sc.next();  // just to stop runtime from exiting. it suspends it
    }
}

If I launch each one from my IDE I get what I want. But now i want to get the same only with launching class2 from class1 (actually many class 2 from class 1 but getting 1 will get me the others). I tried with a class loader but it doesn't work just shares the same console and closing 1 closes the other. Or I did it wrong.

Class1() {
    System.out.println("class1");
    try {
        Class<?> c = ClassLoader.getSystemClassLoader().loadClass("test.Class2");
        c.newInstance();
    } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {
        e.printStackTrace();
    }
    Scanner sc = new Scanner(System.in);
    sc.next();
}

I don't care if i call the constructor of class 2 or its main method as long as it works. but i found out that calling main from 1 class isn't special like when the class loader does it when launching.

I don;t know if i need a new process, a new VM or a new class loader because i don't know how a console is shared and actually i don't think i know the differences. I know that system exit will exit the VM so I think I need to start a new VM? Do i have to? I saw several question on this site on how to do it but it's very ugly and doesn;t look robust.

Most likely they have a reason in this case, but I don't get why people hit-and-run down vote and don't give a reason. — Peter Lawrey, Sep 24 '16 at 19:49
If you want each class to run in its own console and be able to exit independently, you need a process for each one. — Peter Lawrey, Sep 24 '16 at 19:50

score 1 · Accepted Answer · edited May 23 '17 at 10:27

1

Try this in your Class1:

ProcessBuilder pb = new ProcessBuilder("cmd", "/c", "start", "java", "Class2");
pb.start();

This is gonna start a new console and run your Class2.java.

You may need something different than /c, depends what you want, check this out.

edited May 23 '17 at 10:27

Community

1
1

answered Sep 24 '16 at 10:26

Shadov

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1

Yes but this is the same as http://stackoverflow.com/questions/1229605/is-this-really-the-best-way-to-start-a-second-jvm-from-java-code and http://stackoverflow.com/questions/480433/launch-jvm-process-from-a-java-application-use-runtime-exec and http://stackoverflow.com/questions/636367/executing-a-java-application-in-a-separate-process. – Mark Sep 24 '16 at 12:23
@PeterLawrey apparently so. i asked how to do something and the real answer is what you said that i need a new process. as to how to create a new process it was already answered a few times before. i don't know what the site rules are for this. – Mark Oct 09 '16 at 05:16

How to launch an independent java class from another class?

1 Answers1