删除cookie为什么得到的是"null"

Question

创建cookiepublic class TestCookie extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
        Cookie cookie = new Cookie("color","red");
        cookie.setMaxAge(10);
        response.addCookie(cookie);
        out.print("cookie已创建");
} public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);
}
}删除cookiepublic class DeleteCookie extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
Cookie[] cookies = request.getCookies();
 for(Cookie cookie : cookies){
             if(cookie.getName().equalsIgnoreCase("color")){
              cookie.setValue(null);
                 response.addCookie(cookie);
                 out.print("已删除");
                 break;
             }
         }
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);
}
}
检查cookiepublic class TestCookie2 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
PrintWriter out = response.getWriter();
String color = null;
Cookie[] cookies = request.getCookies();
if(cookies != null){
for(Cookie cookie:cookies){
if(cookie.getName().equalsIgnoreCase("color")){
color = cookie.getValue(); 
}
}
}
out.println(color);
out.println("null".equals(color));
          //DeleteCookie删除cookie的时候设置color的值是null，删除后为什么color得到的值是"null"字符串? }
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);
}
}

Answer 1

本帖最后由 java2000_net 于 2011-06-21 15:45:42 编辑

  

Answer 2

 cookie.setValue(null);
//设置为null//字符串null
out.println("null".equals(color));能是一样么？？？

Answer 3

但是打印的是true啊，就是不明白为什么会是true