volley.java

JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, url, null,
        new Response.Listener<JSONObject>() {
            @Override
            public void onResponse(JSONObject response) {
                // handle JSON response
            }
        },
        new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                // handle error
            }
        }
);