how to execute cmd command using another program in java

Question

I want to make a program that open another java programs.how can i run/execute the cmd command in compiling and running java programs.

for example c:\Users\Burnok> javac HelloWorld.java and c:\Users\Burnok> java HelloWorld

how can i do that inside the java program? please help.

I tried this code but it compiled successfully but if i tried to run the HelloWorld.class it says that the could not find or load main class.

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
public class Test {
 private static void printLines(String name, InputStream ins) throws Exception {
 String line = null;
 BufferedReader in = new BufferedReader(
 new InputStreamReader(ins));
 while ((line = in.readLine()) != null) {
 System.out.println(name + " " + line);
 }
 }
 private static void runProcess(String command) throws Exception {
 Process pro = Runtime.getRuntime().exec(command);
 printLines(command + " stdout:", pro.getInputStream());
 printLines(command + " stderr:", pro.getErrorStream());
 pro.waitFor();
 }
 public static void main(String[] args) {
 try {
 runProcess("javac src/HelloWorld.java");
 runProcess("java src/HelloWorld");
 } catch (Exception e) {
 e.printStackTrace();
 }
 }
}

here is the error java src/HelloWorld stderr: Error: Could not find or load main class src.HelloWorld

• sujithvm: Check this stackoverflow.com/questions/4842684/…
• user3276091: i try that but if i tried to run the .class it says that could not find or load main class.
• sujithvm: can you post exactly what you have tried?
• La-comadreja: see mkyong.com/java/how-to-execute-shell-command-from-java
• JustinKSU: Have you checked where HelloWorld.class gets generated and where the current context is when you execute? Is is possible the class file is inside the src directory?

Answer 1

Your are supposed to mention class path while running from another directory

syntax is java -classpath directory_to_program Program

try {
 runProcess("javac src/HelloWorld.java");
 runProcess("java -classpath src HelloWorld");
 } catch (Exception e) {
 e.printStackTrace();
 }

Read for more info How do I run a java program from a different directory?

• user3276091: Thanks it display hello world but i want to run just like the Test class that open another cmd
• sujithvm: @user3276091 sorry can you explain 'that open another cmd' ?
• Dmitry Ginzburg: @user3276091 sujithvm just fixed the bug, not introduced the new way to run, what's the problem then?
• user3276091: yeah but sorry but i want to open another cmd that display helloWorld
• Dmitry Ginzburg: @user3276091 Do you another window with command line to be opened?