MainActivity nestedInArray

package bjd.adrian.gson;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Toast;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.JsonObjectRequest;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;
import com.kosalgeek.asynctask.AsyncResponse;

import org.json.JSONArray;
import org.json.JSONObject;

import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    Double mMid;
    String mMidS;
    String mNo;

    public void showInToast()
    {
        Toast.makeText(this, mNo + mMidS, Toast.LENGTH_LONG).show();
    }

    public void onClick(View view)
    {
        final String TAG = "REQUEST_QUEUE: ";

        final RequestQueue requestQueue = Volley.newRequestQueue(this);

        String url = "http://api.nbp.pl/api/exchangerates/rates/a/eur/?format=json";


        StringRequest stringRequest = new StringRequest(url, new Response.Listener<String>()
        {
            @Override
            public void onResponse(String response)
            {
                Log.v(TAG, response);

                Gson gson = new Gson();

                Post post = gson.fromJson(response, Post.class);

                String code = post.getCode();

                Rates rates = new Rates();

                Double mid = rates.getMid();

                Log.v(TAG, "CODE: "+code + ", MID: "+mid);
            }
        }, new Response.ErrorListener()
        {
            @Override
            public void onErrorResponse(VolleyError error)
            {
                Log.e(TAG, error.toString());
            }
        });

        requestQueue.add(stringRequest);
    }
}