Design Patterns Project Description

This project demonstrates the application of four fundamental design patterns: Factory, Observer, Singleton, and Decorator. The context revolves around a T-Shirt store offering customizable T-Shirts across different regions (Middle East, Asia, and China) and sizes (Small, Medium, and Large). The project highlights a modular and extensible architecture while maintaining design principles.

• Abstract Class: TShirt serves as the base class, containing common attributes like name and description.
• Concrete Classes: There are nine specific classes extending TShirt, each representing a combination of size and region, e.g., AsiaSmallTShirt.

• Abstract Factory: TShirtStore acts as the abstract factory, enforcing the implementation of three methods: createSmallTShirt, createMediumTShirt, and createLargeTShirt.
• Concrete Factories:
  • MiddleEastTShirtStore
  • ChinaTShirtStore
  • AsiaTShirtStore
• Factory Method: The orderTShirt method takes the size as input and ensures the appropriate T-Shirt is returned, tailored to the specified region.

• Abstract Decorator: Features class extends TShirt, enabling additional customizations.
• Concrete Decorators:
  • Logo
  • Text
  • RedColor
  • BlueColor
• Composition: The Features class uses composition to wrap around a TShirt object, allowing dynamic addition of features like colors and text.

• Implementation: The ShopOwner class ensures only a single instance exists by:
  • Making the constructor private.
  • Using a double-checked locking mechanism to manage instance creation.
• Purpose: Centralized control for monitoring sales data and interacting with stores.

• Concrete Subject: TShirtStore keeps track of T-Shirt sales.
• Concrete Observer: ShopOwner subscribes to receive updates on the quantity of T-Shirts sold by size and region.
• Interaction: The ShopOwner is notified whenever a T-Shirt is sold, enabling real-time monitoring.

• Customers can place a single T-Shirt order at a time. Subsequent orders are rejected unless the previous transaction is completed.

1. Initialize ShopOwner: Access the single instance of ShopOwner.
2. Create a T-Shirt Store: Instantiate a store for the desired region (Middle East, Asia, or China).
3. Create a Customer: Instantiate a customer and allow them to place an order.
4. Place an Order:
   • Specify the region, size, and additional customizations (color, logo, text).
   • The system processes the order and notifies the ShopOwner of the sale.

This project demonstrates a robust implementation of design patterns to achieve a flexible, reusable, and scalable architecture. It provides a practical showcase of real-world use cases for these patterns in a domain-specific context.