Question

I wrote a Java program that can execute another Java program during runtime. The program is as follows:

import java.io.*;

public class exec {
    public static void main(String argv[]) {
        int i = 5, j = 6, k = 7;
        BufferedReader rd = new BufferedReader(new InputStreamReader(System.in));    
        try {
            InputStreamReader isr = new InputStreamReader(System.in);
            BufferedReader br = new BufferedReader(isr);
            System.out.println("Enter class name");
            String s = br.readLine();
    
            Process pro = Runtime.getRuntime().exec(s);
    
            BufferedReader in = new BufferedReader(new InputStreamReader(pro.getInputStream()));
            String line=null;
            while((line = in.readLine()) != null) {
                System.out.println(line);
            }
            in.close();
        } catch(Exception err) {
            err.printStackTrace();
        }
    }
}

If I execute this program it will prompt the user to enter any class name (Java program) to execute. This is being done using this piece of code Process pro=Runtime.getRuntime().exec(s);.

Once the user enters the Java class name, I should be able to pass the values 5,6,7 to the Java class entered by the user. Only one value at a time should be passed and the square of that number should be calculated.

How can I do this?

Answer 1

You can pass the int argument to your second Java program as follows:

String[] cmd = { s, Integer.toString(n) };
Process pro=Runtime.getRuntime().exec(cmd);

… or as a single String:

Process pro=Runtime.getRuntime().exec(String.format("%s %d", s, n);