dependencies: #2449 bump maven-checkstyle-plugin from 3.1.0 to 3.2.0 + resolve chec… (#2464)

* #2449 bump maven-checkstyle-plugin from 3.1.0 to 3.2.0 + resolve checkstyle issues

* remove FileSelectorJFrame.java to resolve checkstyle issue

* remove FileSelectorJFrame.java to resolve checkstyle issue

* remove FileSelectorJFrame.java to resolve checkstyle issue

* add refactored file with correct filename to resolve checkstyle issue

* add the test data

* change filenames from JFrame to Jframe for checkstyle

* fix code smell from  sonar report

* add new testcases to improve the test coverage

* remove code smell

event-aggregator/src/main/java/com/iluwatar/event/aggregator/EventEmitter.java

@@ -63,8 +63,8 @@ public abstract class EventEmitter {
   protected void notifyObservers(Event e) {
     if (observerLists.containsKey(e)) {
       observerLists
-        .get(e)
-        .forEach(observer -> observer.onEvent(e));
+          .get(e)
+          .forEach(observer -> observer.onEvent(e));
     }
   }