最近在做一个实验，不过出现了问题解决不了，求高手帮帮忙，感激不尽啊。。。
题目是：猜数字游戏，程序生成一个0~9随机数，玩家有三次机会猜，三次机会之内猜中了提示猜对了，否则提示正确答案并询问是否继续游戏。
下面是我的代码，我感觉会有挺多问题的，但是不知道怎么改，求高手帮忙。。。。
Java code
<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>GuessNumber</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<table width="200" height="100" align="center" border="0"
bgColor="#0080ff">
<tr>
<td>
请猜一个0~9的数字：
</td>
</tr>
<tr>
<td>
<input type="text" maxlength="1" name="guess">
</td>
<td><%=session.getAttribute("answer")%></td>
</tr>
<tr>
<td><%=session.getAttribute("count")%></td>
<td>
<input type="submit" value="确定" name="ok">
</td>
</tr>
</table>
<%
String Guess = new String(request.getParameter("guess").getBytes(
"ISO_8859_1"), "GBK");
int n = 3;
int num = (int) Math.random() * 10;
String count = n + "chances!";
String answer = null;
session.setAttribute("count", count);
while (n != 0) {
if (Guess != null) {
int guess = Integer.parseInt(Guess);
if (num == guess) {
answer = "Congratulation!";
session.setAttribute("answer", answer);
break;
} else {
n--;
answer = "Sorry!You are wrong!";
session.setAttribute("answer", answer);
count = n + "chances!";
session.setAttribute("count", count);
}
} else {
answer = "Please input a number!";
session.setAttribute("answer", answer);
count = n + "chances!";
session.setAttribute("count", count);
}
}
%>
</body>
</html>
运行时出现的问题是：
type Exception report
message?
description
The server encountered an internal error () that prevented it from fulfilling this request.exception?
求sun java 的 serial number，多谢 