Cookie []cookies = request.getCookies();
    boolean b = false;//假设没有 lasttime cookie
    if(cookies != null){
        for(Cookie cookie: cookies){
            String name = cookie.getName();
            if("lasttime".equals(name)){
                out.println("您上次登录时间为"+cookie.getValue());
                SimpleDateFormat simpleDateFormat = new SimpleDateFormat("YYYY-MM-dd HH:mm:ss");
                String nowTime = simpleDateFormat.format(new Date());
                Cookie mycookie = new Cookie("lasttime", nowTime);
                mycookie.setMaxAge(3600);
                response.addCookie(mycookie);
                b = true;
                break;
            }
        }
    }
    if(!b){
        out.println("您是第一次登录");
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("YYYY-MM-dd HH:mm:ss");
        String nowTime = simpleDateFormat.format(new Date());
        Cookie cookie = new Cookie("lasttime", nowTime);
        cookie.setMaxAge(3600);
        response.addCookie(cookie);
    }
}