public static void main(String[] args) {
        String s0 = "?pid=34";
        String s1 = "?pid=34&pageNo=35";
        String s2 = "?pid=56&pageNo=36&sid=23";
        
        //XXXXXXXXXX 正则部分
        
        System.out.println(s0);        //要求输出：?pid=34
        System.out.println(s1);        //要求输出：?pid=34&
        System.out.println(s2);        //要求输出：?pid=56&sid=23
        
        
        /*
         
             提供一个JavaScript的实现参考
            var args = location.search;
            var argName = 'pageNo';
            var reg = new RegExp('([\?&]?)' + argName + '=[^&]*[&$]?', 'gi');
            args = args.replace(reg,'$1');
            alert(args);

         */
    }