Library System Design Patterns

This project is a Java-based Library System that demonstrates the implementation of multiple Design Patterns.

Implemented Design Patterns

1. Singleton

   • Ensures that only one instance of LibraryService exists in the system.

2. Factory

   • BookFactory is used to create different types of books such as:
     • EBook
     • PhysicalBook
     • HistoricalBook

3. Decorator

   • PremiumBookDecorator adds an extra 10 days for borrowing without modifying the original Book class.

4. Proxy

   • PremiumEBookProxy restricts access to EBooks so that only premium users can borrow them.

5. Chain of Responsibility

   • Borrowing requests go through:
     • Librarian
     • Manager

6. Facade

   • LibraryFacade simplifies the borrowing and returning operations by hiding the internal workflow.

7. Adapter

   • BookAdapter converts external book data into the system's Book entity.

8. Observer

   • NotifiableBook notifies registered users when a book becomes available.

Project Features

• Add books to the library
• Borrow and return books
• Support premium books
• Restrict premium eBook access
• Handle borrowing approval flow
• Adapt external book data
• Notify users when books are available

Technologies Used

• Java
• Object-Oriented Programming (OOP)
• Design Patterns

Author

Mohamed Tarek