Cookie抱错

我了一个简单的Cookie,可是却连这么一个简单的Cookie也抱错,我也仔细检查了一下,好象程序也没有什么问题啊!真是郁闷了,望各位大虾帮我看下.<%@ page language="java" contentType="text/html;charset=GB2312"%>
<%@ page import="javax.servlet.http.Cookie,java.util.*"%><%
  String userName = "hellking";
  Cookie[] cookie = request.getCookies();
  Cookie cookie_response = null;
  List list = Arrays.asList(cookie);
  Iterator it = list.iterator();
  while(it.hasNext())
  {
     Cookie temp = (Cookie)it.next();
     if(temp.getName().equals(userName+"_access_time"))
     {
        cookie_response = temp;
        break;
     }
  }
  
  out.println("当前的时间:"+new java.util.Date().toString()+"<br>");
  if(cookie_response!=null)
  {
      out.println("上一次访问的时间:"+cookie_response.getValue());
      cookie_response.setValue(new Date().toString());
  }
  else
  {
      cookie_response = new Cookie(userName+"_access_time",
         new java.util.Date().toString());
  }
  response.addCookie(cookie_response);
  response.setContentType("text/html");
  response.flushBuffer();
 %>以下是抱错信息
java.lang.NullPointerException
at java.util.Arrays$ArrayList.<init>(Arrays.java:3357)
at java.util.Arrays.asList(Arrays.java:3343)
at org.apache.jsp.response_jsp._jspService(response_jsp.java:63)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:390)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:228)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:212)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:634)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:445)
at java.lang.Thread.run(Thread.java:619)
org.apache.jasper.JasperException: An exception occurred processing JSP page /response.jsp at line 9
6:   String userName = "hellking";
7:   Cookie[] cookie = request.getCookies();
8:   Cookie cookie_response = null;
9:   List list = Arrays.asList(cookie);
10:   Iterator it = list.iterator();
11:   while(it.hasNext())
12:   { org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:555)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause java.lang.NullPointerException
java.util.Arrays$ArrayList.<init>(Arrays.java:3357)
java.util.Arrays.asList(Arrays.java:3343)
org.apache.jsp.response_jsp._jspService(response_jsp.java:63)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:390)
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)望各位能够指点