private Double balance;

public double getBalance(Address address){
    balance=0.0;
    String url = urlAPI+address.toString();

    RequestQueue reqQueue;
    reqQueue = Volley.newRequestQueue(this);

JsonObjectRequest jsonObjReq = new JsonObjectRequest(Request.Method.GET, url, null,
            new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {
                    try {

if (response.get("data").toString() != "null") {
                            balance = Double.parseDouble(response.get("data").toString()) / 100000000;
                        } else {
                            balance = 100.00000001;
                        }
                        ;
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                }
            }
    );

reqQueue.add(jsonObjReq);

    return balance;
}