How to correctly draw a UML class diagram with fully qualified association?

Question

Given the following code I have to draw the corresponding class diagram:

public class Shop
{
    List<Client> clients;
    Storage store;
    User chief;
    Set<Invoice> invoices;
}

public class Invoice
{
    Map<Product, Row> rows;
    Client client;
}

public class Client{}
public class Product{}

public class Storage
{
    Map<Integer, Product> products;
}

public class Row 
{
    Product p;
    double qty;
}

On draw.io I produced the following design:

Focus of my question is on - Relation between Invoice and row: Is it correct to draw the qualified association like so? On draw.io I found no option to depict this particular case. I built it by dragging Product class to be adjacent to Invoice.

• Relation between Storage and Product. Is it correct? Or should I represent it also like a qualified association using class Integer as qualifier?

• Do you see any error on relation arrows or cardinality?

Answer 1

I think you need to model Product as a distinct class to make it clear that a Storage may have Products that are not yet included in any Invoice.

You could model Row as an association class for the Invoice-Product association:

Otherwise your diagram seems ok. The structure of Storage seems a bit funny though. If it should keep record of the amount of items, then it probably should have a Map<Product, Integer> instead of Map<Integer, Product>.