Android : Android HTTP Get Params Crashing APP

I'm trying to add GET params to my code so it will append this URL

  "http://sandbox.kriswelsh.com/hygieneapi/hygiene.php?";

to somthing like this

http://sandbox.kriswelsh.com/hygieneapi/hygiene.php?op=nearest&lat=53.472128&long=-2.239928

The params are:

op

nearest

lat

long

Here's my Service handler code which handles the URL and appends the POST and GET methods.

 package com.white.alice.myapplication;
/** HTTP CALL HANDLER **/
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

public class Near {

    static String response = null;
    public final static int GET = 1;
    public final static int POST = 2;

    public Near() {

    }

    public String makeServiceCall(String url, int method) {
        return this.makeServiceCall(url, method, null);
    }

    public String makeServiceCall(String url, int method,
                                  List<NameValuePair> params) {
        try {
            params.add(new BasicNameValuePair("op", "nearest"));
            // http client
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpEntity httpEntity = null;
            HttpResponse httpResponse = null;

            // Checking http request method type
            if (method == POST) {
                HttpPost httpPost = new HttpPost(url);


                // adding post params
                if (params != null) {
                    httpPost.setEntity(new UrlEncodedFormEntity(params));
                }

                httpResponse = httpClient.execute(httpPost);

            } else if (method == GET) {

                // appending params to url
                if (params != null) {
                    String paramString = URLEncodedUtils
                            .format(params, "utf-8");
                    url += "?" + paramString;
                }
                HttpGet httpGet = new HttpGet(url);

                httpResponse = httpClient.execute(httpGet);

            }
            httpEntity = httpResponse.getEntity();
            response = EntityUtils.toString(httpEntity);

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return response;

    }
}

I've already made a List<NameValuePair> params). But each time I try to add a list item or param with params.add(new BasicNameValuePair("key", "value"));. it causes my APP to crash. Am I placing the params.add(new BasicNameValuePair("key", "value")); in the wrong place causing my app to crash? or am I using a incorrect method to add my params to a URL?