Dynamically Reloading a Modified Class : Class Loader « Reflection « Java Tutorial

import java.io.File;
import java.net.URL;
import java.net.URLClassLoader;

class MyClass{
  public String myMethod() {
    return "a message";

public class Main {
  public static void main(String[] argv) throws Exception {

    URL[] urls = null;

    File dir = new File(System.getProperty("user.dir") + File.separator + "dir" + File.separator);
    URL url = dir.toURI().toURL();
    urls = new URL[] { url };

    ClassLoader cl = new URLClassLoader(urls);

    Class cls = cl.loadClass("MyClass");

    MyClass myObj = (MyClass) cls.newInstance();


7.7.Class Loader
7.7.1.URL class loader
7.7.2.extends URLClassLoader
7.7.3.Load classes
7.7.4.how to use reflection to print the names and values of all nonstatic fields of an object
7.7.5.Runs a jar application from any url
7.7.6.BufferedReader reflection
7.7.7.Get the class By way of an object
7.7.8.Get the class By way of a string
7.7.9.Get the class By way of .class
7.7.10.Catch InvocationTargetException
7.7.11.Determining from Where a Class Was Loaded
7.7.12.Dynamically Reloading a Modified Class
7.7.13.Creating an Object Using a Constructor Object
7.7.14.Create an object from a string
7.7.15.Using the forName() method
7.7.16.Context ClassLoader
7.7.17.A tree structure that maps inheritance hierarchies of classes
7.7.18.Analyze ClassLoader hierarchy for any given object or class loader
7.7.19.Instantiate unknown class at runtime and call the object's methods
7.7.20.Load Class