🏧 Mini ATM Simulation

A comprehensive console-based ATM simulation built in Java, demonstrating Object-Oriented Programming principles with persistent data storage.

📋 Table of Contents

• Features
• Technologies Used
• Prerequisites
• Installation
• Usage
• Project Structure
• Class Architecture
• File Storage
• Screenshots
• Contributing
• License

✨ Features

• 💰 Balance Inquiry: Check current account balance
• 📥 Deposit Money: Add funds to your account with validation
• 📤 Withdraw Money: Remove funds with insufficient balance protection
• 📊 Transaction History: View detailed transaction records with timestamps
• 💾 Data Persistence: Account balance and transaction history saved to files
• 🔐 User Authentication: Simple account verification system
• ✅ Input Validation: Robust error handling for all user inputs
• 🎨 Professional UI: Clean, formatted console interface

🛠️ Technologies Used

• Java 11+ (uses String.repeat() method)
• File I/O for data persistence
• Object-Oriented Programming principles
• Collections Framework (ArrayList)
• Java Time API for timestamps

📋 Prerequisites

• Java JDK 11 or higher installed on your system
• Command line interface (Terminal/Command Prompt)
• Text editor or IDE (optional but recommended)

Checking Java Version

java -version
javac -version

If you need to install Java, download from:

• Oracle JDK
• OpenJDK

🚀 Installation

1. Clone the repository

   git clone https://github.com/yourusername/mini-atm-simulation.git
   cd mini-atm-simulation

2. Compile the Java file

   javac ATMSimulation.java

3. Run the application

   java ATMSimulation

💻 Usage

1. Start the application

   java ATMSimulation

2. Enter your credentials

   • Account Number: Enter any account number
   • Account Holder Name: Enter your name

3. Use ATM features

   • Select from the main menu (1-5)
   • Follow on-screen prompts
   • Data is automatically saved after each transaction

Sample Session

**************************************************
*            WELCOME TO MINI ATM            *
**************************************************

Enter Account Number: 12345
Enter Account Holder Name: John Doe

Authentication successful!
Welcome, John Doe!
----------------------------------------

========================================
           ATM MAIN MENU
========================================
1. Check Balance
2. Deposit Money
3. Withdraw Money
4. Transaction History
5. Exit
========================================
Please select an option (1-5): 

📁 Project Structure

mini-atm-simulation/
│
├── ATMSimulation.java      # Main application file
├── balance.txt            # Stores current balance (auto-generated)
├── transactions.txt       # Stores transaction history (auto-generated)
├── README.md             # Project documentation
└── .gitignore           # Git ignore file

🏗️ Class Architecture

🔹 Transaction Class

• Represents individual transactions
• Stores transaction type, amount, timestamp, and resulting balance
• Provides formatted string representation

🔹 Account Class

• Manages account operations and data
• Handles file I/O for balance and transaction persistence
• Validates deposits and withdrawals
• Maintains transaction history

🔹 ATM Class

• Manages user interface and interactions
• Handles menu navigation and user input
• Provides formatted display for all operations
• Includes input validation and error handling

🔹 ATMSimulation Class

• Main application entry point
• Initializes and starts the ATM system

💾 File Storage

The application uses two files for data persistence:

• balance.txt: Stores the current account balance
• transactions.txt: Stores complete transaction history with timestamps

These files are automatically created and updated with each transaction.

📸 Screenshots

Main Menu

========================================
           ATM MAIN MENU
========================================
1. Check Balance
2. Deposit Money
3. Withdraw Money
4. Transaction History
5. Exit
========================================

Transaction History

----------------------------------------------------------------------
                    TRANSACTION HISTORY
----------------------------------------------------------------------
Type       | Amount   | Date & Time         | Balance After
----------------------------------------------------------------------
DEPOSIT    |   500.00 | 2024-01-15 10:30:25 | Balance: $500.00
WITHDRAW   |   100.00 | 2024-01-15 11:45:10 | Balance: $400.00
DEPOSIT    |   250.00 | 2024-01-15 14:20:35 | Balance: $650.00
----------------------------------------------------------------------

🤝 Contributing

Contributions are welcome! Here's how you can help:

1. Fork the repository
2. Create a feature branch

   git checkout -b feature/amazing-feature

3. Commit your changes

   git commit -m 'Add some amazing feature'

4. Push to the branch

   git push origin feature/amazing-feature

5. Open a Pull Request

Contribution Ideas

• Add PIN-based authentication
• Implement multiple account support
• Add account transfer functionality
• Create GUI version using JavaFX/Swing
• Add unit tests
• Implement encryption for data files
• Add transaction limits and daily withdrawal limits

📝 License

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

🎓 Learning Objectives

This project demonstrates:

• Object-Oriented Programming concepts (Encapsulation, Inheritance, Polymorphism)
• File I/O operations in Java
• Exception handling and input validation
• Collections Framework usage
• Java Time API for timestamp management
• Console application development
• Data persistence techniques

🐛 Known Issues

• Transaction history shows only basic formatting in console
• No data encryption for stored files
• Single account support only

🔮 Future Enhancements

• Multi-account support
• PIN-based authentication
• Account-to-account transfers
• Transaction limits
• GUI interface
• Database integration
• Network connectivity for remote ATM access

📞 Support

If you encounter any issues or have questions:

• Open an issue on GitHub
• Check existing issues for solutions
• Review the code comments for implementation details

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