Workshop — OOP 1 (Online Shop)

Objectives

Imagine a very simple online store, similar to an online shop you already know, but much smaller and easier to understand.

In this store, a customer represents a person who wants to buy something.
When the customer decides to buy items, they create an order.
An order represents one purchase made by one customer.

Each order:

• Belongs to exactly one customer
• Can contain one or more products

A product represents an item that can be bought, such as a book or a phone.
Each product has a price.

The main responsibility of the system is to calculate the total price of an order.
This is done by adding together the prices of all products included in that order.

To keep the focus on learning object-oriented concepts, the system includes:

• No database
• No user interface
• No payment handling

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Example Scenario

• A customer named Anna places an order.
• The order contains 10 products, for example:
  • Notebook, pen, backpack, water bottle, calculator
  • Headphones, charger, mouse, USB cable, planner
• Each product has its own price.
• The order calculates the total price by summing the prices of all products.
• The order should also provide a summary of the ordered products, for example:
  • How many products are in the order
  • A list of product names (and optionally their prices)

Important: In this workshop, the design is unidirectional:

• The order knows which customer it belongs to
• The order knows which products it contains
• The customer does not store a list of orders
• The products do not store a reference back to an order

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Your Task

Your task is to complete and implement the design shown in the UML class diagram,
and apply encapsulation and object relationships correctly.

Focus on:

• Creating the correct classes
• Defining the correct fields
• Connecting objects using the relationships shown
• Placing logic in the correct class

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UML Class Diagram (Conceptual)

classDiagram
    class Customer {
        -id:int
        -name:String
        -email:String
    }

    class Product {
        -id:int
        -name:String
        -price:double
    }

    class Order {
        -id:int
        -totalPrice:double
    }

    %% An order belongs to exactly one customer
    Order --> "1" Customer : belongsTo
    %% An order contains one or more products
    Order --> "1..*" Product : contains

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Part 2 — (Optional)

Extend the design by improving the system.

• Add one or more classes or new fields/methods
• Add relationships that make sense in the scenario
• Explain your design choices:
  • What you added
  • Why you added it
  • How it improves the system