[BAEL-6859] inner sub classes (#14631)

* [BAEL-6859] inner and sub classes

* [BAEL-6859] unit test cases added

* [BAEL-6859] usage of inner class in outer class

* [BAEL-6859] usage of inner class in outer class

---------

Co-authored-by: Bhaskar <bhaskar.dastidar@freshworks.com>

core-java-modules/core-java-lang-oop-inheritance/src/main/java/com/baeldung/subclassinnerclass/EmailNotifier.java

@@ -1,11 +1,12 @@
 package com.baeldung.subclassinnerclass;
 
-import java.util.HashMap;
-
 public class EmailNotifier extends Notifier {
     @Override
     void notify(Message e) {
-        // Provide email specific implementation here
+        // connect to the email connector
+        EmailConnector emailConnector = new EmailConnector();
+        emailConnector.connect();
+        // send email
     }
 
     // Inner class for email connection
@@ -13,5 +14,9 @@ public class EmailNotifier extends Notifier {
         private String emailHost;
         private int emailPort;
         // Getter Setters
+
+        private void connect() {
+            // connect to the smtp server
+        }
     }
 }