Question

I have a class named Item. It has the following parameters:
User owner, Category category and String description.

Next to that, I have a subclass named Painting which extends the Item-class. A Painting has two parameters: title and painter.

At some point in the code, I’d like to create a Painting object. It should be possible to run code from a test file that goes like this:

User u1 = new User ("[e-mail]");
Category cat = new Category("cat2");
Item painting = sellerMgr.offerPainting(u1, cat, "Selfportret", "Rembrandt");

There should be code in the class sellerMgr which should be able to register (create) that item (as a Painting), so I can use it in a database for example. How do I call that code exactly? I get confused whenever or not to create a new Item or a new Painting, and which parameters to add in the creation code.

Answer 1

You have a new class

public class Painting extends Item

you’ll want a constructor that provides two new parameters, String title, User painter

public Painting(User owner, Category category, String description, String title, User painter){
    super(owner, category, description);
    this.title = title;
    this.painter = painter
}

Whenever you want a new instance of a Painter you can call this method that will set up any of the Item variables for you, while introducing the two new parameters you desire. A call could look like either

Item paintingAsItem = new Painting(u1, cat, "desc", "Selfportret", "Rembrandt"); //Generic
Painting painting = new Paining(u1, cat, "desc", "Selfportret", "Rembrandt");