Execute another jar in a Java program

The following works by starting the jar with a batch file, in case the program runs as a stand alone:

public static void startExtJarProgram(){
        String extJar = Paths.get("C:\\absolute\\path\\to\\batchfile.bat").toString();
        ProcessBuilder processBuilder = new ProcessBuilder(extJar);
        processBuilder.redirectError(new File(Paths.get("C:\\path\\to\\JavaProcessOutput\\extJar_out_put.txt").toString()));
        processBuilder.redirectInput();
        try {
           final Process process = processBuilder.start();
            try {
                final int exitStatus = process.waitFor();
                if(exitStatus==0){
                    System.out.println("External Jar Started Successfully.");
                    System.exit(0); //or whatever suits 
                }else{
                    System.out.println("There was an error starting external Jar. Perhaps path issues. Use exit code "+exitStatus+" for details.");
                    System.out.println("Check also C:\\path\\to\\JavaProcessOutput\\extJar_out_put.txt file for additional details.");
                    System.exit(1);//whatever
                }
            } catch (InterruptedException ex) {
                System.out.println("InterruptedException: "+ex.getMessage());
            }
        } catch (IOException ex) {
            System.out.println("IOException. Faild to start process. Reason: "+ex.getMessage());
        }
        System.out.println("Process Terminated.");
        System.exit(0);
    }

In the batchfile.bat then we can say:

@echo off
start /min C:\path\to\jarprogram.jar

First we cerate a class FirstFileOutput having a main method that outputs a line to stable output and a line to stable error. With all first procedure, we'll again create a class RuntimeExecCheck that will run our FirstFileOutput class in starting for process, and after that RuntimeExecCheck class will read the stable output and the stable error from FirstFileOutput and output comes.

package check;

public class FirstFileOutput{

    public static void main(String[] args) {
        System.out.println("This is output to stable output");
        System.err.println("This is output to stable error");
    }
}



package check;

import java.io.InputStream;
import java.io.IOException;
import java.io.InputStreamReader;

public class RuntimeExecCheck {

    public static void main(String[] args) {
        try {
            Runtime runTime = Runtime.getRuntime();
            Process process = runTime.exec("java -classpath C:\\projects\\workspace\\check\\bin check.FirstFileOutput");
            InputStream inputStream = process.getInputStream();
            InputStreamReader isr = new InputStreamReader(inputStream);
            InputStream errorStream = process.getErrorStream();
            InputStreamReader esr = new InputStreamReader(errorStream);

            int n1;
            char[] c1 = new char[1024];
            StringBuffer stableOutput = new StringBuffer();
            while ((n1 = isr.read(c1)) > 0) {
                stableOutput.append(c1, 0, n1);
            }
            System.out.println("Stable Output: " + stableOutput.toString());

            int n2;
            char[] c2 = new char[1024];
            StringBuffer stableError = new StringBuffer();
            while ((n2 = esr.read(c2)) > 0) {
                stableError.append(c2, 0, n2);
            }
            System.out.println("Stable Error: " + stableError.toString());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}