Android : How To Follow A Person On Instagram From Our Android App

I am the following code it runs completely without error but not success to follow some one. Answer will be appreciated

 String url = "https://api.instagram.com/v1/users/"+userId+"/relationship?access_token="
           + accessToken;

         HttpClient httpclient = new DefaultHttpClient();
         HttpPost httppost = new HttpPost(url);

         // httppost.setHeader("Accept", "application/json");
         httppost.setHeader("Accept",
           "application/x-www-form-urlencoded");
         // httppost.setHeader("Content-type", "application/json");
         httppost.setHeader("Content-Type",
           "application/x-www-form-urlencoded");

         // Add your data
         List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(
           1);
         nameValuePairs.add(new BasicNameValuePair("action",
           "follow"));
         httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs,
           "UTF-8"));

         try {
          HttpResponse response = httpclient.execute(httppost);

         } catch (Exception e) {
          e.printStackTrace();
         }