这段jsp代码中是有什么问题？

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@page import="java.net.*" %>
<%
out.println("本次访问时间"+new java.util.Date().toLocaleString());
Cookie[] cookies = request.getCookies();
Cookie cookie_response = null;
if(cookies==null){
cookie_response = new Cookie("AccessTime","");
cookie_response.setValue(new java.util.Date().toLocaleString());
URLEncoder.encode("cookie_response", "UTF-8");

response.addCookie(cookie_response);
}else{
URLDecoder.decode("cookie_response", "UTF-8");
cookie_response = cookies[1];
if(cookie_response!=null){
out.println("上一回访问时间"+cookie_response.getValue());
cookie_response.setValue(new java.util.Date().toLocaleString());
}
}
%>

为什么会报java.lang.IllegalArgumentException的错误？

http://blog.csdn.net/linminqin/article/details/6967891