Code cleanup (#1461)

* Code cleanup

* Fix flux tests

* Fix checkstyle errors

* Fix compile error

observer/src/main/java/com/iluwatar/observer/Weather.java

@@ -37,7 +37,7 @@ 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<>();

observer/src/test/java/com/iluwatar/observer/utils/InMemoryAppender.java

@@ -35,7 +35,7 @@ import java.util.List;
  * InMemory Log Appender Util.
  */
 public class InMemoryAppender extends AppenderBase<ILoggingEvent> {
-  private List<ILoggingEvent> log = new LinkedList<>();
+  private final List<ILoggingEvent> log = new LinkedList<>();
 
   public InMemoryAppender(Class clazz) {
     ((Logger) LoggerFactory.getLogger(clazz)).addAppender(this);