code: private void changeValue(String key, String val) {
          String s = readValue(key);
          if (s == null && val == null) {
              return;
          }
          if (s != null && val != null && s.equals(val)) {
              return;
          }
          settingsSync.send(new SettingsSyncActor.ChangeSettings(key, val));
          onUpdatedSetting(key, val);
          notifySettingsChanged();
      }
docs: Sync methods