HelloClassLoader.java

package com.baoge.jvm;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Base64;

public class HelloClassLoader extends ClassLoader {
    public static void main(String[] args) {

        try {
            ClassLoader classLoader = new HelloClassLoader();
            //  动态 加载相应的类
            Class<?> clazz = classLoader.loadClass("Hello");
            Object instance = clazz.newInstance();
            // 调用实例方法
            Method method = clazz.getMethod("hello");
            method.invoke(instance);
        } catch (InstantiationException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
    }

    @Override
    protected Class<?> findClass(String name) throws ClassNotFoundException {
        String helloBase64 = "NQFFQf///8v/4/X/+f/x9v/w/+/3/+71/+3/7Pj/6/j/6v7/+cOWkZaLwf7//NfWqf7/+7yQm5r+" +
                "//CzlpGasYqSnZqNq56dk5r+//qXmpOTkP7/9ayQio2cmrmWk5r+//W3mpOTkNGVnome8//4//f4" +
                "/+nz/+j/5/7/7Leak5OQ09+ck56MjLOQnpuajd74/+bz/+X/5P7/+reak5OQ/v/vlZ6JntCTnpGY" +
                "0LCdlZqci/7/75WeiZ7Qk56RmNCshoyLmpL+//yQiov+/+qzlZ6JntCWkNCvjZaRi6yLjZqeksT+" +
                "/+yVnome0JaQ0K+NlpGLrIuNmp6S/v/4j42WkYuTkf7/6tezlZ6JntCTnpGY0KyLjZaRmMTWqf/e" +
                "//r/+f///////f/+//j/9//+//b////i//7//v////rVSP/+Tv////7/9f////n//v////7//v/0" +
                "//f//v/2////2v/9//7////2Tf/97fxJ//tO/////v/1////9f/9////+//3//r//v/z/////f/y";
        byte[] bytes = this.decode(helloBase64);

        return defineClass(name, bytes, 0, bytes.length);
    }
    public byte[] decode(String base64){

        byte[] byteArray = Base64.getDecoder().decode(base64);
        byte[] targetArray = new byte[byteArray.length];
        for (int i = 0; i < byteArray.length; i++) {
            targetArray[i] = (byte) (255 - byteArray[i]);
        }
        return targetArray;
    }
}