import java.io.File; import java.lang.reflect.Method; import java.net.URL; import java.net.URLClassLoader; public class TestAddUrl { public static void main(String[] args) throws Exception { URLClassLoader classLoader = (URLClassLoader) TestAddUrl.class.getClassLoader(); String dir = "./lib"; Method method = URLClassLoader.class.getDeclaredMethod("addURL", URL.class); method.setAccessible(true); method.invoke(classLoader, new File(dir).getAbsoluteFile().toURL()); Class klass = Class.forName("HelloKimmking",true, classLoader); Object obj = klass.newInstance(); Method hello = klass.getDeclaredMethod("hello"); hello.invoke(obj); } }