Executing a Java application in a separate process

This might be an overkill for you, but Project Akuma does what you want and more. I found it via this entry at Kohsuke's (one of Sun's rock start programmers) fabulously useful blog.

Two hints:

System.getProperty("java.home") + "/bin/java" gives you a path to the java executable.

((URLClassLoader) Thread.currentThread().getContextClassLoader()).getURL() helps you to reconstruct the classpath of current application.

Then your EXECUTE.application is just (pseudocode):

Process.exec(javaExecutable, "-classpath", urls.join(":"), CLASS_TO_BE_EXECUTED)

This is a synthesis of some of the other answers that have been provided. The Java system properties provide enough information to come up with the path to the java command and the classpath in what, I think, is a platform independent way.

public final class JavaProcess {

    private JavaProcess() {}        

    public static int exec(Class klass, List<String> args) throws IOException,
                                               InterruptedException {
        String javaHome = System.getProperty("java.home");
        String javaBin = javaHome +
                File.separator + "bin" +
                File.separator + "java";
        String classpath = System.getProperty("java.class.path");
        String className = klass.getName();

        List<String> command = new LinkedList<String>();
        command.add(javaBin);
        command.add("-cp");
        command.add(classpath);
        command.add(className);
        if (args != null) {
            command.addAll(args);
        }

        ProcessBuilder builder = new ProcessBuilder(command);

        Process process = builder.inheritIO().start();
        process.waitFor();
        return process.exitValue();
    }

}

You would run this method like so:

int status = JavaProcess.exec(MyClass.class, args);

I thought it made sense to pass in the actual class rather than the String representation of the name since the class has to be in the classpath anyways for this to work.