get android ad id

x.java

       AsyncTask<Void, Void, String> task = new AsyncTask<Void, Void, String>() {
            @Override
            protected String doInBackground(Void... params) {
                AdvertisingIdClient.Info idInfo = null;
                try {
                    idInfo = AdvertisingIdClient.getAdvertisingIdInfo(getApplicationContext());
                } catch (GooglePlayServicesNotAvailableException e) {
                    e.printStackTrace();
                } catch (GooglePlayServicesRepairableException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                String advertId = null;
                try{
                    advertId = idInfo.getId();
                }catch (NullPointerException e){
                    e.printStackTrace();
                }

                return advertId;
            }

            @Override
            protected void onPostExecute(String advertId) {
                Toast.makeText(getApplicationContext(), advertId, Toast.LENGTH_SHORT).show();
            }

        };
        task.execute();