类的加载机制(代码片段)

protected ClassLoader(ClassLoader parent) 
    SecurityManager security = System.getSecurityManager();
    if (security != null) 
        security.checkCreateClassLoader();
    
    this.parent = parent;
    initialized = true;

    protected ClassLoader() 
    SecurityManager security = System.getSecurityManager();
    if (security != null) 
        security.checkCreateClassLoader();
    
    this.parent = getSystemClassLoader();
    initialized = true;
    

public Class<?> loadClass(String name) throws ClassNotFoundException 
    return loadClass(name, false);
    
    protected synchronized Class<?> loadClass(String name, boolean resolve)
    throws ClassNotFoundException
    
    // First, check if the class has already been loaded
    Class c = findLoadedClass(name);
    if (c == null) 
        try 
       if (parent != null) 
           c = parent.loadClass(name, false);
        else 
           c = findBootstrapClass0(name);
       
         catch (ClassNotFoundException e) 
            // If still not found, then invoke findClass in order
            // to find the class.
            c = findClass(name);
        
    
    if (resolve) 
        resolveClass(c);
    
    return c;

package com.pony.cl;

public class Test 
    public void hello() 
        System.out.println("恩，是的，我是由 " + getClass().getClassLoader().getClass()
                + " 加载进来的");
    

import java.io.FileInputStream;
import java.lang.reflect.Method;

public class Main 
    static class MyClassLoader extends ClassLoader 
        private String classPath;

        public MyClassLoader(String classPath) 
            this.classPath = classPath;
        

        private byte[] loadByte(String name) throws Exception 
            name = name.replaceAll("\\\\.", "/");
            FileInputStream fis = new FileInputStream(classPath + "/" + name
                    + ".class");
            int len = fis.available();
            byte[] data = new byte[len];
            fis.read(data);
            fis.close();
            return data;

        

        protected Class<?> findClass(String name) throws ClassNotFoundException 
            try 
                byte[] data = loadByte(name);
                return defineClass(name, data, 0, data.length);
             catch (Exception e) 
                e.printStackTrace();
                throw new ClassNotFoundException();
            
        

    ;

    public static void main(String args[]) throws Exception 
        MyClassLoader classLoader = new MyClassLoader("D:/test");
        Class clazz = classLoader.loadClass("com.pony.cl.Test");
        Object obj = clazz.newInstance();
        Method helloMethod = clazz.getDeclaredMethod("hello", null);
        helloMethod.invoke(obj, null);
    

Object obj = clazz.newInstance();
不能写成：
Test obj = (Test)clazz.newInstance();