💸 UPI Wallet Engine (Java)

A Java-based console application that simulates a UPI Wallet System using clean OOPS principles, layered architecture, and service-based design.

This project demonstrates how real-world digital wallet systems work internally, including user management, wallet balance handling, secure PIN-based transactions, and transaction history tracking.

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🚀 Features

• 👤 Create User Account
• 💰 Add Money to Wallet
• 🔎 View Wallet Balance
• 🔐 Send Money with PIN Verification
• 🔁 Transfer Money Between Users
• 📜 View Transaction History
• 🧱 Clean Layered Architecture (Model, Service, Util, Main)
• 🛡️ Basic Security using PIN Authentication

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🛠️ Technologies & Concepts Used

• Java
• OOPS (Encapsulation, Abstraction, Composition)
• Collections Framework (HashMap, ArrayList)
• Service Layer Architecture
• In-Memory Data Storage
• Package-based Project Structure
• Git & GitHub

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🏗️ Project Structure

UPI-Wallet-Engine-Java/
 ├── Main.java
 ├── Model/
 │    ├── User.java
 │    ├── Wallet.java
 │    └── transaction.java
 ├── service/
 │    ├── UserService.java
 │    └── WalletService.java
 ├── util/
 │    └── DataStore.java
 ├── .gitignore
 └── Readme.md

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▶️ How to Run the Project

1️⃣ Clone the repository:

git clone https://github.com/pranav440/UPI-Wallet-Engine-Java.git

2️⃣ Open in VS Code / IntelliJ / Eclipse

3️⃣ Run:

Main.java

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🧪 How the System Works

1. Create users using name, mobile number, and PIN

2. Add money to wallet

3. Send money to another user (PIN required)

4. System checks:

   • Sender exists
   • Receiver exists
   • PIN is correct
   • Balance is sufficient

5. Transaction is recorded in history

6. You can view all transactions anytime

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🧠 Core Concepts Implemented

• Encapsulation (User controls PIN verification)
• Separation of Concerns (Main, Service, Model, Util)
• In-memory Database using HashMap
• Business Logic Layer
• Transaction Logging System

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📈 Future Improvements

• 💾 File-based data persistence
• 🔒 Account lock after 3 wrong PIN attempts
• 📊 Stream API based transaction reports
• 🧾 Transaction filtering (date-wise, user-wise)
• 🌐 Web version using Spring Boot
• 🗄️ Database integration (MySQL)

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👨‍💻 Author

Pranav Ganorkar Java Developer | Backend Enthusiast 🚀

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⭐ If you like this project

Give it a ⭐ on GitHub and feel free to fork and improve it!

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