Hi I am woring for a Quiz App, so I need to call post rest services(json),below one is my sample code which is not working

I need to pass 3 thing as parameter 1-userid, 2-List questionids and 3- List answerIds. My Question is how to pass List Object not String or Json String here-

List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
    nameValuePairs.add(new BasicNameValuePair("userid", "121213"));
    nameValuePairs.add(new BasicNameValuePair("questionsids", listobj);
    nameValuePairs.add(new BasicNameValuePair("answerIds", listObj));

    HttpClient httpclient=new DefaultHttpClient();
    HttpPost httppost = new HttpPost(url);
    httppost.setHeader(HTTP.CONTENT_TYPE,"application/x-www-form-urlencoded;charset=UTF-8");

    try {
        httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs, "UTF-8"));
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    }

Is There any other way to call the post rest service.How to resolve above one?

Thanks Ranjan.