Java Design Patterns

A comprehensive collection of 23 classic design patterns implemented in Java with detailed documentation, examples, and educational resources.

🎯 Overview

This repository serves as a complete learning resource for Java design patterns. Each pattern is:

• ✅ Fully implemented with working code examples
• ✅ Well-documented with detailed explanations
• ✅ Educational with class diagrams and usage examples
• ✅ Production-ready with proper JavaDocs and comments

📚 Implemented Patterns

🏗️ Creational Patterns (5)

Patterns that deal with object creation mechanisms

• Factory Method - Create objects without specifying exact classes
• Singleton - Ensure only one instance exists
• Abstract Factory - Create families of related objects
• Builder - Construct complex objects step by step
• Prototype - Clone existing objects

🏛️ Structural Patterns (7)

Patterns that deal with object composition and relationships

• Decorator - Add behavior to objects dynamically
• Adapter - Make incompatible interfaces work together
• Bridge - Split abstraction from implementation
• Composite - Treat individual and composite objects uniformly
• Facade - Provide simplified interface to complex subsystem
• Flyweight - Share common parts of state between objects
• Proxy - Provide substitute or placeholder for another object

🎭 Behavioral Patterns (11)

Patterns that deal with communication between objects

• Chain of Responsibility - Pass requests along handler chain
• Command - Encapsulate request as object
• Interpreter - Define grammar representation and interpreter
• Iterator - Access collection elements without exposing structure
• Mediator - Reduce coupling between components
• Memento - Save and restore object state
• Observer - Notify multiple objects about events
• State - Alter object behavior when state changes
• Strategy - Define family of algorithms
• Template Method - Define algorithm skeleton in method
• Visitor - Separate algorithms from objects

🚀 Getting Started

Prerequisites

• Java 8 or higher
• Maven (for building)

Quick Start

# Clone the repository
git clone https://github.com/shihabcsedu09/java-design-patterns.git

# Navigate to the project
cd java-design-patterns

# Build the project
mvn compile

📖 How to Use

1. Browse Patterns: Each pattern has its own folder under src/main/java/
2. Read Documentation: Every pattern includes a detailed README with:
   • Pattern explanation and purpose
   • Implementation details
   • Class diagrams (Mermaid)
   • Usage examples
   • When to use guidance
3. Run Examples: Each pattern has a main App.java file demonstrating usage
4. Study Code: Well-commented code with JavaDoc for learning

🎓 Learning Path

Beginner Level

Start with these fundamental patterns:

1. Singleton - Basic object creation control
2. Factory Method - Simple object creation
3. Observer - Event handling
4. Strategy - Algorithm selection

Intermediate Level

Move to more complex patterns:

1. Decorator - Dynamic behavior addition
2. Command - Request encapsulation
3. State - State-dependent behavior
4. Template Method - Algorithm structure

Advanced Level

Explore sophisticated patterns:

1. Visitor - Operation separation
2. Interpreter - Language interpretation
3. Mediator - Complex communication
4. Flyweight - Memory optimization

🛠️ Project Structure

src/main/java/
├── creational/          # Object creation patterns
├── structural/          # Object composition patterns
└── behavioral/          # Communication patterns
    ├── pattern-name/
    │   ├── App.java     # Main demonstration
    │   ├── README.md    # Pattern documentation
    │   └── ...          # Pattern-specific classes

📝 Contributing

We welcome contributions! Here's how you can help:

1. Report Issues: Found a bug or have a suggestion? Open an issue
2. Add Patterns: Implement additional design patterns
3. Improve Documentation: Enhance READMEs or add more examples
4. Code Quality: Suggest improvements to existing implementations

Contribution Guidelines

• Follow existing code style and structure
• Add comprehensive documentation for new patterns
• Include class diagrams and usage examples
• Test your implementations thoroughly

📄 License

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

🙏 Acknowledgments

• Inspired by the Gang of Four (GoF) design patterns
• Built for educational purposes and learning
• Community-driven improvements and feedback

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Happy Learning! 🎉

Master the art of software design with these proven patterns.