WalletOne: Virtual Credit Card Management System

WalletOne is a robust Java-based virtual credit card management system designed for efficient handling of card information, user data, and related operations, all in the command-line interface (CLI). For a detailed description and overview of WalletOne's main functionalities, see this blog post: Introducing WalletOne: An Interactive Java Backend App Featuring a Virtual Credit Card Management System.

Key Features

• Add and remove credit cards with unique card numbers
• Manage multiple users per card
• Search functionality by zip code and user name
• Display detailed card information
• Constant-time card lookup using hash-based data structures
• Efficient user management with multi-key indexing

Technical Highlights

• Constant-time Card Lookup: Utilizes HashMap for O(1) card retrieval by card number
• Multi-key Indexing: Implements separate HashMaps for zip code and name-based user lookups
• Memory-efficient User Storage: Uses a shared User object across different indexes
• HashMap-based Card Storage: The CardManager class uses a HashMap<String, Card> (cardHashMap) for O(1) card retrieval by card number.
• Scalable Architecture: Designed to handle a large number of cards and users efficiently

Installation

1. Ensure you have Java Development Kit (JDK) 8 or higher installed on your system.
2. Clone the repository:

git clone https://github.com/chriseborowski/walletone.git

3. Navigate to the project directory:

cd walletone

4. Compile the Java files:

javac -d bin src/walletone/*.java

Usage

1. Run the main application:

java -cp bin walletone.Main

2. Follow the on-screen prompts to interact with the system.

Class Structure

• Card: Represents a credit card with associated users
• User: Represents a card user with name and zip code
• CardManager: Core class managing all card operations and user lookups
• Main: Entry point of the application (not provided in the context, but assumed to exist)

Key Methods

• addNewCard: Adds a new card to the system
• removeCard: Removes a card and updates all related data structures
• addUserToCard: Adds a new user to an existing card
• searchByZip: Retrieves users by zip code
• searchByName: Retrieves users by name
• showAllCards: Displays information for all cards in the system

Performance Considerations

• Card lookup: O(1) time complexity
• User lookup by zip code or name: O(1) average case, O(n) worst case where n is the number of users with the same zip code or name
• Adding/Removing cards: O(1) time complexity
• Adding users to a card: O(1) amortized time complexity

Future Enhancements

• Implement data persistence (database integration)
• Add user authentication and authorization
• Develop a graphical user interface (GUI)
• Implement card transaction tracking and analysis

Contributing

Contributions are welcome! Please feel free to submit a pull request.

License

This project is licensed under the MIT License - see the LICENSE.md file for details.