Add all 23 GoF design pattern implementations (2026-06-13)

02-structural/flyweight/Main.java

@@ -0,0 +1,50 @@
+package flyweight;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+
+/**
+ * Flyweight Design Pattern — Runnable Demo
+ *
+ * Creates 1000 trees of only 3 species. Without Flyweight: 1000 TreeType
+ * objects. With Flyweight: 3 TreeType objects (one per species), shared.
+ *
+ * Run: javac flyweight/*.java && java flyweight.Main
+ * Article: https://ankurm.com/flyweight-design-pattern-java/
+ */
+public class Main {
+
+    public static void main(String[] args) {
+        System.out.println("=== Flyweight Design Pattern Demo ===\n");
+
+        List<Tree> forest = new ArrayList<>();
+        Random rnd = new Random(42);
+
+        String[][] treeSpecs = {
+            {"Oak",  "dark-green", "rough-bark"},
+            {"Pine", "blue-green", "needle-texture"},
+            {"Birch","light-green","smooth-white-bark"}
+        };
+
+        System.out.println("Creating 1,000 trees (only 3 TreeType objects should be created):");
+        for (int i = 0; i < 1000; i++) {
+            String[] spec = treeSpecs[i % 3];
+            TreeType type = TreeFactory.getTreeType(spec[0], spec[1], spec[2]);
+            forest.add(new Tree(rnd.nextInt(800), rnd.nextInt(600), type));
+        }
+
+        System.out.println("\nForest created. Drawing first 5 trees:");
+        for (int i = 0; i < 5; i++) {
+            forest.get(i).draw();
+        }
+
+        System.out.println("\n--- Memory summary ---");
+        System.out.println("Trees in forest    : " + forest.size());
+        System.out.println("Unique TreeType objects in pool: " + TreeFactory.getPoolSize());
+        System.out.println("Without Flyweight  : 1,000 TreeType objects");
+        System.out.println("With Flyweight     : " + TreeFactory.getPoolSize() + " TreeType objects shared");
+
+        System.out.println("\n=== Demo complete ===");
+    }
+}