🛒 Java Online Store System

This project was developed as part of a semester-long Object-Oriented Programming (OOP) course.
It simulates a basic e-commerce platform written entirely in Java, showcasing class hierarchy, modular structure, and exception handling.

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🎯 Project Overview

The system allows buyers and sellers to interact in a virtual marketplace:

• Buyers can register, browse products, add items to their cart, and place orders
• Sellers can add products to their inventory
• Each order is recorded with date and total price
• Cart cloning and order history supported
• Handles invalid inputs and custom exceptions

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💡 Key Features

• 👤 User management – Registration of buyers and sellers
• 🛍️ Product catalog – Multiple categories and optional packaging
• 🧺 Cart & Order – Add/remove items, checkout, track history
• 🔁 Cart cloning – Restore past orders into current cart
• 🧾 Order summary – Date, items, price
• ⚠️ Custom exceptions – Empty cart, invalid strings, negative numbers
• 📦 OOP principles – Encapsulation, inheritance, composition
• 🧪 Tested via console interface

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📁 Package & Class Structure

All classes are under the package:

package onlinestore;
| Class                            | Description                                          |
|----------------------------------|------------------------------------------------------|
| `Main.java`                      | Runs the program and presents the menu               |
| `Buyer.java`                     | Represents a buyer with cart and orders              |
| `Seller.java`                    | Represents a seller with product list                |
| `Product.java`                   | Base class for store items                           |
| `PackagedProduct.java`           | Product with extra packaging cost                    |
| `Order.java`                     | Represents an order with timestamp & items           |
| `Address.java`                   | Location data for buyers                             |
| `SystemManager.java`             | Core logic for users, products, actions              |
| `ProductList.java`               | Internal list to store products                      |
| `User.java`                      | Common base class for Buyer & Seller                 |
| `eCategory.java`                 | Enum for product categories                          |
| `StringEmptyNullException.java`  | Thrown for empty/null strings                        |
| `NegativeNumException.java`      | Thrown for invalid numbers                           |
| `EmptyCartException.java`        | Thrown when trying to buy from an empty cart         |

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🛠️ Compilation & Execution״

To compile and run the project from terminal:

javac onlinestore/*.java
java onlinestore.Main

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📷 Example Menu Output

Welcome to IYR 🛍️
1) Add a seller
2) Add a buyer
3) Add a product for the seller
4) Add a product for the buyer
5) Pay for your products
6) Show buyers
7) Show sellers
8) Show products by category
9) Clone cart from history
0) Exit

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🧠 What I Learned

• Designing modular Java applications using OOP
• Creating interactive command-line menus
• Exception handling for domain-specific logic
• Deep use of inheritance, composition, and encapsulation
• Managing user input and validating system behavior

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👤 Author

Itamar Hadad
B.Sc. Computer Science Student – Afeka Tel Aviv Academic College of Engineering
Email: [email protected]
LinkedIn: https://www.linkedin.com/in/itamar-hadad

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