🧑‍💻 Console Based User Registration & Login System (Java)

A simple console-based authentication system built using Core Java concepts like OOP, Collections and basic service layer design.

This project simulates how a real application handles:

1.User Registration

2.User Login

3.Duplicate Username Validation

4.Viewing Registered Users (for demo purpose)

It is designed as a beginner friendly project to understand application flow and separation of responsibilities before moving to JDBC / Database based systems.

📂 Project Structure com.daksh.userapp

│

├── MainApp.java → Handles user interaction (UI / Menu)

├── User.java → Model class (User entity)

└── UserService.java → Business logic & data handling

⚙️ Features 🔐 Registration

-> Accepts username, password and email

-> Prevents duplicate usernames

-> Stores user in memory (ArrayList)

🔑 Login

-> Validates username and password

-> Displays welcome message on success

-> Shows error on invalid credentials

📋 Show All Users (Demo)

-> Displays all registered users

-> Helps verify stored data

🧠 Concepts Used

-> Classes & Objects (OOP)

-> Encapsulation (Private fields + getters)

-> ArrayList (Dynamic Data Storage)

-> Loops & Conditional Logic

-> Layered Design (UI → Service → Model)

-> Basic Authentication Logic