设计一个类加载器

类加载器用于实现类的加载动作，但它在Java程序中起到的作用远远不限于类加载阶段。对于任何一个类，都需要由加载它的类加载器和这个类本身来决定其在Java虚拟机中的唯一性

package com.study.classLoad;

import java.io.IOException;
import java.io.InputStream;
/**
 * 设计一个简单的类加载器
 * @author xiaojuan
 *
 */
public class ClassLoaderTest {

    public static void main(String[] args) throws InstantiationException, IllegalAccessException, ClassNotFoundException {
        // TODO Auto-generated method stub
        ClassLoader myLoader = new ClassLoader(){

            @Override
            public Class<?> loadClass(String name)
                    throws ClassNotFoundException {
                try {
                    //String filename = "com.study.classLoad.ClassLoaderTest";
                    String filename = name.substring(name.lastIndexOf(".") + 1) + ".class";
                    InputStream is = getClass().getResourceAsStream(filename);
                    if (is == null) {
                        return super.loadClass(name);
                    }
                    byte[] b = new byte[is.available()];
                    is.read(b);
                    return defineClass(name, b, 0, b.length);
                } catch (IOException e) {
                    throw new ClassNotFoundException();
                }
                
            }
            
        };
        Object obj = myLoader.loadClass("com.study.classLoad.ClassLoaderTest").newInstance();
        System.out.println(obj.getClass());
        System.out.println(obj instanceof com.study.classLoad.ClassLoaderTest);
        
    }

}