get device id for facebook ad test

facebook.java

    public class customTask extends AsyncTask<Void, String, String> {


        @Override
        protected void onPreExecute() {
            super.onPreExecute();
        }

        @Override
        protected String doInBackground(Void... voids) {

            AdvertisingIdClient.Info adInfo = null;
            try {
                adInfo = AdvertisingIdClient.getAdvertisingIdInfo(getApplicationContext());
            } catch (IOException e) {
                // ...
            } catch (GooglePlayServicesNotAvailableException e) {
                e.printStackTrace();
            } catch (GooglePlayServicesRepairableException e) {
                e.printStackTrace();
            }
            String userId = adInfo.getId();

            return userId;
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);

            Log.d("FACEBOOK_ID", "" + s.toString());
        }
    }
    
    
    and it will execute like this 
    
    
        new customTask().execute();