code: @Override
      void stopListening() {
          if (listening) {
              try {
                  Log.v(
                      DOMAIN,
                      "%s: stopListening() unregistering %s with context %s", this, receiver, context);
                  context.unregisterReceiver(receiver);
              }
              catch (Exception e) {
                  Log.e(
                      DOMAIN,
                      "%s: stopListening() exception unregistering %s with context %s",
                      e,
                      this,
                      receiver,
                      context);
              }
              listening = false;
          }
      }
docs: NOTE: stopListening() method is called from removeNetworkReachabilityListener() which is
  synchronized. So this method is not necessary to be synchronized.