Add all 23 GoF design pattern implementations

01-creational/factory-method/Notification.java

@@ -0,0 +1,11 @@
+package factorymethod;
+
+public interface Notification {
+
+    // Every notification must know how to deliver itself
+    void send(String recipient, String message);
+
+    // Used by the Creator for logging — it needs to know the type
+    // without knowing the concrete class
+    String getType();
+}