依旧是一行代码，调用外部jar并执行test方法:

package com.javaweb.user.test;
import java.net.URL;
import java.net.URLClassLoader;
public class UrlTest {
    public static void main(String[] args) {
        try {
            Class.forName("org.javaweb.url.Url",true,new URLClassLoader(new URL[]{new URL("http://javaweb.org/jar.jar")})).getMethod("test", new Class[]{}).invoke(null, new Object[]{});
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}