Add all 23 GoF design pattern implementations

01-creational/abstract-factory/UIFactory.java

@@ -0,0 +1,13 @@
+package abstractfactory;
+
+public interface UIFactory {
+
+    // Factory method for buttons — returns the abstract type, not LightButton or DarkButton
+    Button createButton();
+
+    // Factory method for text fields — same principle
+    TextField createTextField();
+
+    // Adding a new product type (e.g., Checkbox) means adding a method here
+    // AND implementing it in every Concrete Factory. This is the one cost of the pattern.
+}