getting data directly from server

AlumnusListActivity.java

/**
 * Created by omayib on 18/09/17.
 */

public class AlumnusListActivity extends Activity{
    private static final String TAG = "AlumnusListActivity";
    private RecyclerView mRecyclerView;
    private LinearLayoutManager mLinearLayoutManager;
    private RecyclerAdapter mAdapter;
    private ArrayList<Person> alumnus;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_alumni_list);

        mRecyclerView = (RecyclerView) findViewById(R.id.recyclerViewAlumni);
        mLinearLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mLinearLayoutManager);
        alumnus = new ArrayList<>();

        mAdapter = new RecyclerAdapter(alumnus);
        mRecyclerView.setAdapter(mAdapter);


        loadDataFromServer();


    }

    private void loadDataFromServer() {
        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder().url("http://10.0.2.2:3000/alumnus").build();

        client.newCall(request).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                e.printStackTrace();
            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                try {
                    JSONArray data = new JSONArray(response.body().string());
                    for (int i = 0; i < data.length(); i++) {
                        JSONObject obj = data.getJSONObject(i);
                        alumnus.add(new Person(obj.getString("id"),obj.getString("name"),obj.getString("email"),obj.getString("work")));
                   }
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            mAdapter.notifyDataSetChanged();
                        }
                    });
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}