Java Class Hot Deploy

import java.net.URL;
import java.net.URLClassLoader;
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class Client
{
 static ClassLoader cl;
 static ServerItf server;

 public static void loadNewVersionOfServer() throws Exception{
  URL serverURLs[] = new URL[]{new URL("file:server/")};//新版本文件放置地点
  cl = new URLClassLoader(serverURLs);//创建类载入器
  server = (ServerItf)cl.loadClass("ServerImpl").newInstance();//载入制定类并生成实例
 }

 public static void test() throws Exception{
  BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
  loadNewVersionOfServer();
  while (true)
  {
   System.out.println("Enter QUOTE,RELOAD,GC, or QUIT: ");
   String cmdRead = br.readLine();
   String cmd = cmdRead.toUpperCase();
   if (cmd.equals("QUIT"))//退出程序
   {
    return;
   }else if (cmd.equals("QUOTE"))//
   {
    System.out.println(server.getQuote());
   }else if (cmd.equals("RELOAD"))//载入新类
   {
    loadNewVersionOfServer();
    System.gc();//要求虚拟机回收旧类装载器
    System.runFinalization();
   }
   else if (cmd.equals("GC"))
   {
    System.gc();
    System.runFinalization();
   }
  }
 }

 public static void main(String args[]) {
  try
  {
   test();
  }
  catch (Exception e)
  {
   e.printStackTrace();
  }
 }
};

public interface ServerItf {
 public String getQuote();
}

class Reporter
{
 Class cls;
 Reporter(Class cls) {
  this.cls = cls;
  System.out.println("ServerImpl class "+cls.hashCode()+" loaded into VM");
 }

 protected void finalize(){
  System.out.println("ServerImpl class "+cls.hashCode()+" unloaded from VM");
 }
};

public class ServerImpl implements ServerItf
{
 static Object reporter = new Reporter(ServerImpl.class);
 public String getQuote(){ return " A rolling stong gathers no moss";}
 }
};