# 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

```bash
# Linux / macOS / Git Bash (Windows)
javac 03-behavioral/strategy/*.java -d out/strategy
java -cp out/strategy strategy.Main
```

```cmd
REM Windows Command Prompt
javac 03-behavioral\strategy\*.java -d out\strategy
java -cp out\strategy strategy.Main
```

## 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