RequestsHelper for volley

RequestsHelper.java

public class RequestsHelper {

    private RequestQueue mRequestQueue;
    private ImageLoader mImageLoader;
    private static RequestsHelper mInstance;
    private static Context ctx;

    public static synchronized RequestsHelper getInstance(Context context) {
        if (mInstance == null)
            mInstance = new RequestsHelper(context);

        return mInstance;
    }

    public RequestsHelper(Context context) {
        ctx = context;
        mRequestQueue = getRequestQueue();
        mImageLoader = new ImageLoader(mRequestQueue,
                new ImageLoader.ImageCache() {
                    private final LruCache<String, Bitmap> cache = new LruCache<>(20);
                    @Override public Bitmap getBitmap(String url) {
                        return cache.get(url);
                    }

                    @Override public void putBitmap(String url, Bitmap bitmap) {
                        cache.put(url, bitmap);
                    }
                });
    }

    public void makePostRequest(String baseUrl, String id, final Map<String, String> params,
                                Response.Listener<String> responseListener, Response.ErrorListener errorListener) {
        String url = baseUrl + id;
        makeAndSubmitRequest(url, Request.Method.POST, params, responseListener, errorListener);

        
    }

    public void makeGetRequest(String url, final Map<String, String> params,
                                Response.Listener<String> responseListener, Response.ErrorListener errorListener) {
        makeAndSubmitRequest(url, Request.Method.GET, params, responseListener, errorListener);
    }

    public void makeAndSubmitRequest(String url, int method, final Map<String, String> params,
                                      Response.Listener<String> responseListener, Response.ErrorListener errorListener) {
        submitRequest(makeRequest(url, method, params, responseListener, errorListener));
    }

    public StringRequest makeRequest(String url, int method, final Map<String, String> params,
                             Response.Listener<String> responseListener, Response.ErrorListener errorListener) {
        StringRequest stringRequest = new StringRequest(method, url, responseListener, errorListener){
            @Override
            protected Map<String, String> getParams(){ return params; }
        };
        stringRequest.setRetryPolicy(new DefaultRetryPolicy(0, -1, DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
       return stringRequest;
    }

    public void submitRequest(StringRequest request) {
        getRequestQueue().add(request);
    }

    public ImageLoader getImageLoader() {
        return mImageLoader;
    }

    public RequestQueue getRequestQueue() {
        if (mRequestQueue == null) {
            Cache cache = new DiskBasedCache(ctx.getCacheDir(), 10 * 1024 * 1024);
            Network network = new BasicNetwork(new HurlStack());
            mRequestQueue = new RequestQueue(cache, network);
            // Don't forget to start the volley request queue
            mRequestQueue.start();
        }
        return mRequestQueue;
    }
}