How to run two classes at a time in CMD in Java

Question

Hello I create one java file which contains two classes TwoClass and TwoClass2 On compilation it gives me two class files separately but I have to run each class file separately.. How can I do this ? My code is as follows: I saved this file as TwoClass.java

class TwoClass{
public static void main(String args[])
{
    System.out.println("I am first class");
}}class TwoClass2{
public static void main(String args[])
{
    System.out.println("I am Second class");
}}

After compilation it generates TwoClass.class and TwoClass2.class Now if I want to run this files I do as follows:

G:\\ZPREP>javac TwoClass.java

G:\\ZPREP>java TwoClass I am first class

G:\\ZPREP>java TwoClass2 I am Second class

G:\\ZPREP>

There is no problem here at all but I have to run each file separately so any thing is their to run both files at a time ??? Please help.

Answer 1

Rather than trying to do it in the command line, use a third class to run two threads, one per class, so both your classes' main method will run at the same time, using the same args ; something like this:

class TwoclassMain {

    public static void main(final String ... args) {

        Runnable runnableOne = new Runnable {
            public void run() { TwoClass.main(args); }
        }

        Runnable runnableTwo = new Runnable {
            public void run() { TwoClass2.main(args); }
        }

        Thread one = new Thread(runnableOne);
        Thread two = new Thread(runnableTwo);

        one.start();
        two.start();

        one.join();
        two.join();
    }

}

DISCLAIMER: I haven't compiled and run this example, is just to show the general idea.

UPDATE: Same idea using Java 8:

class TwoclassMain {

    public static void main(final String ... args) {

        Thread one = new Thread(() -> TwoClass.main(args));
        Thread two = new Thread(() -> TwoClass2.main(args));

        one.start();
        two.start();

        one.join();
        two.join();
    }

}

Answer 2

On the command line you can chain commands with && . After each command completes successfully the next will run. Eg,

javac TwoClass.java && java TwoClass && java TwoClass2

Or you could have one main method call the other:

class TwoClass {
    public static void main(String args[]) {
        System.out.println("I am first class");
        TwoClass2.main(args);
    }
}

Or write a third to call them both:

class Foo {
    public static void main(String args[]) {
        TwoClass.main(args);
        TwoClass2.main(args);
    }
}