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

README.md

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+# GoF Design Patterns in Java
+
+Complete runnable Java 17 implementations of all 23 Gang of Four design patterns. Each pattern has a dedicated article at [ankurm.com](https://ankurm.com/gof-design-patterns-java/) with a UML diagram, step-by-step explanation, and console output.
+
+## Structure
+
+```
+design-patterns/
+├── 01-creational/
+│   ├── factory-method/
+│   ├── abstract-factory/
+│   ├── builder/
+│   ├── prototype/
+│   └── singleton/
+├── 02-structural/
+│   ├── adapter/
+│   ├── bridge/
+│   ├── composite/
+│   ├── decorator/
+│   ├── facade/
+│   ├── flyweight/
+│   └── proxy/
+└── 03-behavioral/
+    ├── chain-of-responsibility/
+    ├── command/
+    ├── interpreter/
+    ├── iterator/
+    ├── mediator/
+    ├── memento/
+    ├── observer/
+    ├── state/
+    ├── strategy/
+    ├── template-method/
+    └── visitor/
+```
+
+## Prerequisites
+
+- Java 17+ (Eclipse Temurin recommended)
+- No build tool required — plain `javac` / `java`
+
+## Run any pattern
+
+```powershell
+# Windows (PowerShell)
+$JAVAC = 'C:\Program Files\Eclipse Adoptium\jdk-17.0.7.7-hotspot\bin\javac.exe'
+$JAVA  = 'C:\Program Files\Eclipse Adoptium\jdk-17.0.7.7-hotspot\bin\java.exe'
+
+& $JAVAC 03-behavioral/strategy/*.java -d out/strategy
+& $JAVA -cp out/strategy strategy.Main
+```
+
+```bash
+# Linux / macOS
+javac 03-behavioral/strategy/*.java -d out/strategy
+java -cp out/strategy strategy.Main
+```
+
+## Run all behavioral patterns (Windows)
+
+Double-click `RUN-behavioral.bat` or run in PowerShell:
+
+```powershell
+powershell -ExecutionPolicy Bypass -File run-behavioral.ps1
+```
+
+## Articles
+
+| Pattern | Category | Article |
+|---------|----------|---------|
+| Factory Method | Creational | https://ankurm.com/factory-method-design-pattern-java/ |
+| Abstract Factory | Creational | https://ankurm.com/abstract-factory-design-pattern-java/ |
+| Builder | Creational | https://ankurm.com/builder-design-pattern-java/ |
+| Prototype | Creational | https://ankurm.com/prototype-design-pattern-java/ |
+| Singleton | Creational | https://ankurm.com/singleton-design-pattern-java/ |
+| Adapter | Structural | https://ankurm.com/adapter-design-pattern-java/ |
+| Bridge | Structural | https://ankurm.com/bridge-design-pattern-java/ |
+| Composite | Structural | https://ankurm.com/composite-design-pattern-java/ |
+| Decorator | Structural | https://ankurm.com/decorator-design-pattern-java/ |
+| Facade | Structural | https://ankurm.com/facade-design-pattern-java/ |
+| Flyweight | Structural | https://ankurm.com/flyweight-design-pattern-java/ |
+| Proxy | Structural | https://ankurm.com/proxy-design-pattern-java/ |
+| Chain of Responsibility | Behavioral | https://ankurm.com/chain-of-responsibility-design-pattern-java/ |
+| Command | Behavioral | https://ankurm.com/command-design-pattern-java/ |
+| Interpreter | Behavioral | https://ankurm.com/interpreter-design-pattern-java/ |
+| Iterator | Behavioral | https://ankurm.com/iterator-design-pattern-java/ |
+| Mediator | Behavioral | https://ankurm.com/mediator-design-pattern-java/ |
+| Memento | Behavioral | https://ankurm.com/memento-design-pattern-java/ |
+| Observer | Behavioral | https://ankurm.com/observer-design-pattern-java/ |
+| State | Behavioral | https://ankurm.com/state-design-pattern-java/ |
+| Strategy | Behavioral | https://ankurm.com/strategy-design-pattern-java/ |
+| Template Method | Behavioral | https://ankurm.com/template-method-design-pattern-java/ |
+| Visitor | Behavioral | https://ankurm.com/visitor-design-pattern-java/ |
+
+## Reference
+
+- *Design Patterns: Elements of Reusable Object-Oriented Software* — Gamma, Helm, Johnson, Vlissides
+- https://refactoring.guru/design-patterns