Desktop Java base class.

Foo.java

package com.example;

import java.io.InputStream;
import java.net.URLClassLoader;
import java.util.jar.Manifest;

public class Foo {

    public void bar() {
    }

    public static void main(String[] args) throws Exception {
        URLClassLoader loader = (URLClassLoader) Foo.class.getClassLoader();
        String command = System.getProperty("sun.java.command");
        int index = command.indexOf(" ");
        if (index > -1) {
            command = command.substring(0, index);
        }
        if (command.toLowerCase().endsWith(".jar")) {
            try (InputStream in = loader
                    .findResource("META-INF/MANIFEST.MF")
                    .openStream()) {
                command = new Manifest(in)
                        .getMainAttributes()
                        .getValue("Main-Class");
            }
        }
        Foo foo = (Foo) loader.loadClass(command).newInstance();
        foo.bar();
    }
}