Tomat出错,帮忙看看

org.apache.jasper.JasperException: Index: 0, Size: 0
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:370)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
java.util.ArrayList.RangeCheck(ArrayList.java:547)
java.util.ArrayList.get(ArrayList.java:322)
com.wind.taglib.UserUpdate.doStartTag(UserUpdate.java:24)
org.apache.jsp.manage.user_005fUpdate_jsp._jspService(org.apache.jsp.manage.user_005fUpdate_jsp:92)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:322)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.12 logs.下标越界:
源码如下:
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { request.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
String userID=request.getParameter("userID").trim();
out.println(userID);//测试有id
String name=request.getParameter("userName").trim();
out.println(name);//测试有name
String pwd=request.getParameter("userPwd");
out.println(pwd);//测试为null
String xm=request.getParameter("userXM").trim();
String card=request.getParameter("userCard");
String role=request.getParameter("userRole");
String state=request.getParameter("userState");

if(userID!=null && userID!="" && name!=null && name!="" && 
pwd!=null && pwd!="" && xm!=null && xm!="" && card!=null && card!="" && 
role!=null && role!="" && state!=null && state!=""){
DatabaseResultSet dbrs=new DatabaseResultSet();
String sql="update tb_User set userPwd='" + pwd + "',userXM='"+ xm +"',userCard='"+ card +"',userRole="+ role +",userState="+ state+" where userID="+userID;
if(dbrs.updateDatabaseBySqlstr(sql)){
out.println("<script>alert('修改成功');window.location='/TestJsp/manage/user_Manage.jsp';</script>");
}else{
out.println("<script>alert('修改未成功!');window.location='/TestJsp/manage/user_Update.jsp';</script>");
}
}else{
out.println("<script>alert('请输入完整的信息!');window.location='/TestJsp/manage/user_Update.jsp';</script>");
}
out.close();
}