A multi-threaded, console-based banking application that simulates core banking operations with a focus on thread safety and concurrency handling.

• Overview
• Features
• Architecture
• Project Structure
• Console UI Features
• Threading Model
• How to Run
• Sample Operations
• Handling Concurrency
• Error Handling

This application demonstrates a banking system that allows users to create accounts, deposit and withdraw funds, transfer money between accounts, and check balances - all in a thread-safe environment that handles concurrent operations properly.

• Account Management: Create bank accounts with unique account numbers
• Deposit & Withdrawal: Thread-safe deposit and withdrawal operations
• Fund Transfers: Transfer funds between accounts with proper synchronization
• Balance Inquiry: Check account balances securely
• Colorful UI: Enhanced console interface with colors and formatting
• Multi-threading: Execute operations concurrently using thread pool
• Proper Error Handling: Comprehensive exception management

The application follows a layered architecture pattern:

┌─────────────────┐
│  Presentation   │ Controller layer handling user interaction
├─────────────────┤
│    Service      │ Business logic implementation
├─────────────────┤
│   Repository    │ Data access layer
├─────────────────┤
│     Model       │ Domain objects
└─────────────────┘

BankApplication/
├── BankApp.java                  # Application entry point
├── controller/
│   └── BankController.java       # Handles user interactions and menu
├── service/
│   ├── BankService.java          # Banking service interface
│   └── BankServiceImpl.java      # Banking service implementation
├── repository/
│   ├── AccountRepository.java    # Account repository interface
│   └── InMemoryAccountRepository.java # In-memory implementation
├── model/
│   └── Account.java              # Account entity with thread-safe operations
├── exception/
│   ├── AccountNotFoundException.java
│   └── InsufficientFundsException.java
└── util/
    └── ConsoleUtils.java         # Utility for enhanced console display

The application uses ConsoleUtils to provide an enhanced console experience:

• Color-coded Output: Different colors for different message types
• Formatted Headers: Styled headers for different sections
• Success/Error Indications: Visually distinguishable success and error messages
• Interactive Menus: Well-formatted menu options
• Progress Indicators: Visual feedback for operations
• Tabular Data: Data displayed in formatted tables
• Welcome Banner: Attractive welcome screen

The application uses a thread pool (ExecutorService) to handle concurrent operations:

• Core banking operations run in separate threads
• Synchronized blocks prevent race conditions during transfers
• Thread-safe collections store account data
• Atomic operations within the Account class

1. Compile all Java files:

   javac -d bin d:\Java_Practice\System_Design_13\BankApplication\*.java
   

2. Run the application:

   java -cp bin BankApp
   

3. Follow the on-screen menu to interact with the banking system

==== Create Account ====

Enter account number: 1001
✓ Account created successfully

==== Deposit Funds ====

Account number: 1001
Amount: 500
✓ Deposit successful

==== Check Balance ====

Account number: 1001
┌──────────────────┐
│ Balance: $500.0  │
└──────────────────┘

==== Transfer Funds ====

From Account: 1001
To Account: 1002
Amount: 200
✓ Transfer successful

The application handles concurrent access to accounts using:

1. Synchronized Methods: Core Account methods are synchronized
2. Lock Ordering: When transferring between accounts, locks are acquired in a consistent order
3. Thread Pool: Operations are executed through a managed thread pool
4. Thread-safe Collections: ConcurrentHashMap stores account data

The application handles various error conditions:

• Account Not Found: When operations reference non-existent accounts
• Insufficient Funds: When withdrawal/transfer amounts exceed balance
• Invalid Input: Validation for input parameters
• Visual Feedback: Color-coded error messages in the console UI