#113 Event Driven Architecture

- added class diagram
- added more comments

event-driven-architecture/src/main/java/com/iluwatar/eda/App.java

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+package com.iluwatar.eda;
+
+import com.iluwatar.eda.event.Event;
+import com.iluwatar.eda.event.UserCreatedEvent;
+import com.iluwatar.eda.event.UserUpdatedEvent;
+import com.iluwatar.eda.handler.UserCreatedEventHandler;
+import com.iluwatar.eda.handler.UserUpdatedEventHandler;
+
+/**
+ * An event-driven architecture (EDA) is a framework that orchestrates behavior around the production,
+ * detection and consumption of events as well as the responses they evoke.
+ * An event is any identifiable occurrence that has significance for system hardware or software.
+ * <p/>
+ * The example below we uses an {@link EventDispatcher} to link/register  {@link Event} objects to
+ * their respective handlers Once an {@link Event} is dispatched,
+ * it's respective handler is invoked and the {@link Event} is handled accordingly
+ */
+public class App {
+
+    public static void main(String[] args) {
+        EventDispatcher dispatcher = new EventDispatcher();
+        dispatcher.registerChannel(UserCreatedEvent.class, new UserCreatedEventHandler());
+        dispatcher.registerChannel(UserUpdatedEvent.class, new UserUpdatedEventHandler());
+        dispatcher.dispatch(new UserCreatedEvent());
+        dispatcher.dispatch(new UserUpdatedEvent());
+    }
+
+}