🧩 Advanced Programming: Java Design Patterns

A structured, hands-on reference for Advanced Design Patterns in Java — built for developers who want to master object-oriented design, clean architecture, and real-world problem solving.

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📌 About

Design patterns are proven, reusable solutions to recurring software design problems. This repository provides:

• ✅ Clean, well-documented Java implementations
• ✅ Realistic, practical examples for each pattern
• ✅ Organized package structure under com
• ✅ Ready-to-run Main classes for immediate experimentation

Whether you're preparing for technical interviews, leveling up your architecture skills, or simply exploring OOP principles — this repo has you covered.

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📂 Project Structure

DesignPatterns/
│── src/
│   └── com/
│       ├── singleton/        # Creational
│       ├── factory/          # Creational
│       ├── decorator/        # Structural
│       ├── observer/         # Behavioral
│       ├── strategy/         # Behavioral
│       ├── command/          # Behavioral
│       └── ...               # More patterns coming soon
│
└── README.md

Each package contains:

• Pattern implementation class(es)
• A Main.java entry point to run the example
• Inline comments explaining the design decisions

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🏗️ Implemented Patterns

Category	Pattern	Description
Creational	Singleton	Ensures a class has only one instance
Structural	Decorator	Adds behavior to objects dynamically
Behavioral	Observer	Notifies dependents of state changes
Behavioral	Strategy	Defines a family of interchangeable algorithms
Behavioral	Command	Encapsulates requests as objects

🔄 More patterns will be added progressively as the repository grows.

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🚀 Getting Started

Prerequisites

• Java JDK 8 or higher
• Any Java-compatible IDE: IntelliJ IDEA, Eclipse, or VS Code

Installation

1. Clone the repository:

git clone https://github.com/your-username/DesignPatterns.git

2. Open the project in your preferred IDE.

3. Navigate to the pattern you want to explore:

src/com/<pattern-name>/

4. Run the Main class to see the pattern in action.

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💡 Example: Singleton Pattern

The Singleton pattern ensures only one instance of a class is created and provides a global access point to it.

package com.singleton;

public class Singleton {
    private static Singleton instance;

    private Singleton() {}

    public static Singleton getInstance() {
        if (instance == null) {
            instance = new Singleton();
        }
        return instance;
    }
}

// Usage
Singleton s1 = Singleton.getInstance();
Singleton s2 = Singleton.getInstance();

System.out.println(s1 == s2); // true — same instance

⚠️ The above uses a basic (non-thread-safe) implementation. See the source for a thread-safe version using synchronized or double-checked locking.

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🎯 Goals & Use Cases

• 📚 Learn and apply advanced design patterns in Java
• 🔨 Improve object-oriented design and architectural thinking
• 💼 Prepare for technical interviews and system design discussions
• 🏛️ Build scalable, maintainable, and extensible software

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🤝 Contributing

Contributions are welcome! To add a new pattern or improve an existing one:

1. Fork the repository
2. Create a branch for your feature: git checkout -b feature/pattern-name
3. Commit your changes: git commit -m "Add: <PatternName> pattern"
4. Push to your fork: git push origin feature/pattern-name
5. Open a Pull Request for review

Please follow the existing package structure and include a Main.java with a working example.

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📜 License

This project is open-source and available under the MIT License.

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⭐ Support

If you find this project helpful, consider giving it a ⭐ on GitHub — it helps others discover it too!