急急急急！！！！

battier 2007-10-21 10:16:27

在运行JSP文件时，出现以下错误：</script>
19: </HEAD>
20:
21: <%
22: int usernum=0;
23: String act="";
24: String face="";

Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:524)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:435)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

root cause

java.lang.NullPointerException
org.apache.jsp.getinfo_jsp._jspService(getinfo_jsp.java:85)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

原程序为：<%@ page contentType="text/html;charset=gb2312" %>
<%@ page import="java.util.*" %>
<HTML>
<HEAD>
<TITLE> 用户信息 </TITLE>
<META NAME="Author" CONTENT="jj">
<script language="JavaScript">

</script>
</HEAD>

<%
int usernum=0;
String act="";
String face="";
String nick="";
String sex="";
String qq="";
String email="";//定义变量

String name=(String) session.getValue("userid");;
Hashtable userlist =(Hashtable)application.getAttribute("userlist");
Enumeration aa=userlist.elements(); //获取在线用户
usernum=userlist.size();
%>

<BODY bgcolor="#99CCFF" onkeydown="">
<meta http-equiv =refresh content="8">
<form action="/" name="userlist">
<Div align=center>
<BR>
<BR>
<FONT SIZE="2" >[<A href="getinfo.jsp">刷新用户列表</A>]
</Div><BR>
[在线用户:<font color=red><%=usernum%><B></B></font>人]
<HR>
<% int index=0;

while(aa.hasMoreElements()){ //罗列各个用户的信息
index++;
act=( String ) aa.nextElement();
int i = act.indexOf("++");
if(i!=-1) {
nick=act.substring(0,i);
act =act.substring(i+2); }
i = act.indexOf("++");
if(i!=-1) {
face=act.substring(0,i);
act =act.substring(i+2); }
i = act.indexOf("++");
if(i!=-1) {
sex=act.substring(0,i);
act =act.substring(i+2); }
i = act.indexOf("++");
if(i!=-1) {
qq=act.substring(0,i);
act =act.substring(i+2); } //由拼接的信息提取各个部分
//html完成显示
email=act;
%>
<DIV onClick="menuclick(member<%= index %>);PerformSubmit('<%= nick %>');" width="15" height="15"style="CURSOR: hand">
<img src="images/
<% if (nick.equals(name)) out.print("me");
else if (sex.equals("0"))out.print("gg");
else out.print("mm");%>.gif" >
<%= nick %></div>
<DIV id=member<%= index %> style="DISPLAY: none; ">
<IMG SRC="images/face<%= face%>.gif" WIDTH="32" HEIGHT="32" BORDER=0 ALT=""> <B><U><I><%= nick %></I></U></B><BR><B>QQ</B>:<%= qq %><BR>
<B>Email</B>:<%= email %><BR>
</div>
<%
}
%>
</FONT>
<HR>
</form></FONT>
</BODY>
</HTML>
请问是什么原因？？？

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