🎯 Java Design Patterns Showcase

This repository demonstrates key Software Design Patterns in Java, grouped by category:

• Creational
• Structural
• Behavioral

Each pattern is implemented as an individual, self-contained project with minimal code and maximum clarity — designed for both learning and reference.

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📁 Project Structure

design-patterns-java/
├── creational/
│   ├── singleton/
│   │   └── LoggerModule.java
│   ├── builder/
│   │   └── UserModule.java
│   └── abstract-factory/
│       └── UIGenerator.java
├── structural/
│   ├── facade/
│   │   └── HomeTheaterSystem.java
│   └── adapter/
│       └── MusicPlayer.java
└── behavioral/
    ├── strategy/
    │   └── NavigatorModule.java
    └── observer/
        └── WeatherApplication.java

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🧱 Creational Patterns

🔹 Singleton

Ensures a class has only one instance and provides a global point of access to it.

✅ Key Concepts:

• Private constructor
• Static instance
• Thread-safe (with double-checked locking)

🔹 Builder

Builds complex objects step-by-step without using telescoping constructors.

✅ Key Concepts:

• Immutable object creation
• Chainable setter methods
• build() method

🔹 Abstract Factory

Creates families of related objects without specifying concrete classes.

✅ Key Concepts:

• Factory of factories
• Consistency across product families (e.g., Mac UI vs Windows UI)

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🧩 Structural Patterns

🔹 Facade

Provides a simplified interface to a complex subsystem.

✅ Key Concepts:

• Hides complexity
• Single entry point
• Ideal for APIs and libraries

🔹 Adapter

Allows incompatible interfaces to work together.

✅ Key Concepts:

• Converts one interface to another
• Useful for integrating legacy code

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🔁 Behavioral Patterns

🔹 Strategy

Defines a family of algorithms, encapsulates each one, and makes them interchangeable at runtime.

✅ Key Concepts:

• Interface-based design
• Replace logic at runtime
• Promotes flexibility

🔹 Observer

Defines a one-to-many dependency between objects — when one changes, all dependents are notified.

✅ Key Concepts:

• Publisher-subscriber model
• Real-time notifications
• Loosely coupled components

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🚀 How to Run

Each pattern resides in its own folder with a dedicated Main.java. You can:

1. Open the folder in your IDE (e.g., IntelliJ, Eclipse)
2. Run Main.java
3. Observe the output in the console

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🛠 Technologies Used

• Java 17 (or compatible version)
• No external dependencies
• IDE-agnostic folder structure

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📚 Resources for Further Learning

• Refactoring.Guru
• Design Patterns: Elements of Reusable Object-Oriented Software (GoF)
• Head First Design Patterns

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🤝 Contributing

Feel free to fork, modify, and submit pull requests. If you have ideas for additional patterns or examples, contributions are welcome!

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📄 License

This project is licensed under the MIT License.

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📌 Author

Dinesh Kumar Gopinathan

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