Banking System – Java Mini Project

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Overview

This is a console-based Java Banking System built as part of the Virtusa Full Stack Development Program Mini Project.
It demonstrates Object-Oriented Programming, Collections Framework, Multithreading, and Exception Handling in a real-world scenario.

Users can create accounts, perform deposits, withdrawals, transfers, and even simulate concurrent transactions using multiple threads.

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🧩 Features

Create a new bank account
Deposit / Withdraw / Transfer money
Show account balance
Prevent invalid or duplicate account creation
Handle errors gracefully with custom exceptions
Thread-safe operations using ConcurrentHashMap
Demonstrate multithreading with ExecutorService
Layered architecture – Model, Service, and Main packages
Functional programming (Streams / Lambda) used for validation

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📂 Project Folder Structure

com/
└── bank/
 ├── model/
 │ ├── Account.java
 │ └── SavingsAccount.java (Inheritance demo)
 │
 ├── service/
 │ ├── AccountService.java (Interface – abstraction)
 │ └── AccountServiceImpl.java (Implementation – polymorphism)
 │
 ├── exceptions/
 │ ├── AccountNotFoundException.java
 │ ├── InvalidAmountException.java
 │ ├── InvalidNameException.java
 │ └── InsufficientBalanceException.java
 │
 ├── utils/
 │ └── AccountNumGenerator.java
 │
 └── main/
  ├── Main.java
  ├── AccountOperationsMenu.java
  └── AccountOperations.java

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⚙️ Technologies & Concepts Used

Concept	Description
OOP	Classes, Objects, Abstraction (Interface), Polymorphism, Encapsulation, Inheritance
Collections	Used ConcurrentHashMap<String, Account> for thread-safe account storage
Generics	Strongly typed collections (Map<String, Account>)
Functional Programming	Used Streams and Lambda expressions (anyMatch(), ExecutorService)
Multithreading	Used ExecutorService, Runnable, and synchronized blocks
Exception Handling	Custom exceptions with meaningful messages
Synchronization	Ensures thread safety during concurrent deposits/withdrawals
Layered Architecture	Clear separation: Model → Service → Main (UI)
Input Validation	Handled with try-catch and specific exception blocks

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Menu Options

Main Menu

1. Create Account
2. Perform Operations on Existing Account
3. Exit

Account Menu

1. Deposit
2. Withdraw
3. Transfer
4. Show Balance
5. Simulate Concurrent Transactions
6. Back to Main Menu

🧠 Exceptions

All exceptions are handled gracefully with proper user messages.