一个Cookie的问题

一个简单的Cookie登陆程序：
<%@page import="javax.servlet.http.Cookie;"%>
<%  
  String username="";
  String pwd="";
  
  Cookie[] c = request.getCookies();
  for(int i=0;i<=c.length;i++){
    if("username".equals(c[i].getName()))
      username = c[i].getValue();
    if("pwd".equals(c[i].getName()))
      pwd = c[i].getValue();
%>
报错如下：
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:451)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:373)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
root cause java.lang.ArrayIndexOutOfBoundsException: 2
org.apache.jsp.Cookie.index_jsp._jspService(index_jsp.java:58)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)