How to run external java program using java?

Question

Question is to abstract.

I want to run java code using java but the thing is java code may take input from console using (Scanner or other methods...)

import java.util.Scanner;
public class Main{
    public static void main(String args[]){
        Scanner scanner = new Scanner(System.in);
        int i = scanner.nextInt();
        System.out.println(i);
    }
}

I tried running below program for this thing but it neither gives me error nor showing any output.

import java.util.Scanner;
import java.io.*;

public class MyExec {
    public static void main(String[] args)
    {
        //init shell
        ProcessBuilder builder = new ProcessBuilder( "/bin/bash" );
        Process p=null;
        try {
            p = builder.start();
        }
        catch (IOException e) {
            System.out.println(e);
        }
        //get stdin of shell
        BufferedWriter p_stdin = 
          new BufferedWriter(new OutputStreamWriter(p.getOutputStream()));

            try {
                //single execution
                    p_stdin.write("javac Main.java");
                    p_stdin.newLine();
                    p_stdin.flush();
                    p_stdin.write("java Main.class");
                    p_stdin.newLine();
                    p_stdin.flush();
                    p_stdin.write("1");
                    p_stdin.newLine();
                    p_stdin.flush();
            }
            catch (IOException e) {
            System.out.println(e);
            }
        

        // finally close the shell by execution exit command
        try {
            p_stdin.write("exit");
            p_stdin.newLine();
            p_stdin.flush();
        }
        catch (IOException e) {
            System.out.println(e);
        }

    // write stdout of shell (=output of all commands)
    Scanner s = new Scanner( p.getInputStream() );
    while (s.hasNext())
    {
        System.out.println( s.next() );
    }
       s.close();
    }
}

I want to pass inputs too How to figure the mistake out, Don't know what thing is going wrong here

Answer 1

you can read response of command executed as below

         ProcessBuilder pb = new ProcessBuilder();
            pb.command(cmd);
            Process proc = pb.start();
            proc.waitFor();

            InputStream inputStream = proc.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
            String responseLine = "";
            StringBuilder output = new StringBuilder();
            while (( responseLine = reader.readLine())!= null) {
                output.append(responseLine + "\n");
            }