Code cleanup (#1461)

* Code cleanup

* Fix flux tests

* Fix checkstyle errors

* Fix compile error

observer/README.md

@@ -99,7 +99,7 @@ public class Weather {
   private static final Logger LOGGER = LoggerFactory.getLogger(Weather.class);
 
   private WeatherType currentWeather;
-  private List<WeatherObserver> observers;
+  private final List<WeatherObserver> observers;
 
   public Weather() {
     observers = new ArrayList<>();