Grocery_System (GrocerySystem_01.java)

A simple console-based grocery store application written in Java. It provides categories and items, allows customers to add items to a cart, modify or clear the cart, and generate a bill with payment options (Cash, Card, UPI).

This README explains how to compile and run the program, lists features and limitations, and suggests improvements.

Features

• Category-based item browsing (Dairy, Snacks, Bakery, Vegetables, Fruits, Hygiene, Beverages)
• View product stock and prices
• Add items to cart (quantity tracking)
• View and modify cart (change item quantities)
• Clear cart (restores stock)
• Generate bill with:
  • Automatic total calculation
  • Discounts for totals and payment methods
  • Payment methods:
    • Cash (no discount)
    • Card (5% discount)
    • UPI (10% discount, shows a QR image if qrcode.png exists)
• Basic input validation for numeric fields (mobile, card number, CVV)

Prerequisites

• Java Development Kit (JDK) 8 or later
• Terminal or console for running the program
• Optional: qrcode.png in the project directory to be shown for UPI payment

Notes:

• The application uses ANSI color escape sequences for console styling. Some terminals (for example, older Windows Command Prompt) may not render these colors correctly. Use a terminal that supports ANSI escape codes (Windows Terminal, PowerShell with ANSI support, Linux/macOS terminals) or remove/adjust color constants in the source code.

Files

• GrocerySystem_01.java — Main program (console application)
• Optional: qrcode.png — QR image shown during UPI payment (place in project root)

How to build and run

1. Save the GrocerySystem_01.java file in a directory.

2. Open a terminal in that directory.

3. Compile:

   javac GrocerySystem_01.java

4. Run:

   java GrocerySystem_01

Follow on-screen prompts to enter your name, mobile number, navigate categories, add items, and complete the purchase.

Usage tips

• Enter numeric values when prompted (mobile number, menu choices, quantities, payment details).
• Mobile number validation requires exactly 10 digits.
• Card number validation requires exactly 16 digits with Luhn Algo for Card Number Validation, CVV requires exactly 3 digits.
• To use the UPI option and see a QR code dialog, place a valid qrcode.png image file in the same directory before running. The app uses Swing JOptionPane to display the QR.

Known issues and limitations

(This section documents some behaviors you may observe and ideas for improvement.)

• initialStocks array: The code currently initializes initialStocks with dimensions new int[stocks.length][stocks.length]. This may not match the rectangular shape of stocks and could be revised to new int[stocks.length][stocks[0].length] or by copying row-by-row (the code does clone rows, but the declaration size is uneven).
• Cart price recalculation in modifyCart uses (cartPrices[index] / currentQuantity) * newQuantity. If currentQuantity were ever 0 this would cause division by zero — in usual flows currentQuantity > 0, but defensive checks would be good.
• Program flow: The code sometimes calls Categories() from within manageCart() which can create nested loops and complexity of control flow (re-entrant menu calls). Consider converting to a single main loop to simplify navigation.
• No persistent storage: All data (stock, cart) is in-memory; restarting the program resets stock and cart.
• Multi-user / concurrency: Not supported (single-user console app).
• Input robustness: While numeric validation exists, some edge cases may still cause unexpected behavior (e.g., using non-digit characters in some scanf calls).
• Terminal Base(No - UI) - As it is a simple learning project.

Suggested improvements

• Improve program control flow (single main loop, return codes instead of nested calls).
• Add persistent storage (file-based or database) to track stock between runs.
• Add better error handling and unit tests.
• Replace fixed size cart arrays with dynamic lists (ArrayList) to avoid fixed limits.
• Extract product and cart item into classes for better object-oriented design.
• Improve UI (simple GUI or web frontend) for better user experience.
• Add localization support and currency formatting.

Contributing

If you'd like to contribute:

• Fork the repository and create a branch for your changes.
• Make improvements, fix bugs, or add features (see Suggested improvements).
• Open a pull request describing your changes.

License

MIT.