Implementing domain model

Question

Hello everyone,
I am not sure if this is the most suitable forum to ask this question, but here i go:
I am developing an online auction application with hibernate. I am learning hibernate with the book "Hibernate in action" and following the example.
In this example there is a class called Category (has a many to many relation with Item class) and look like this:
public class Category implements Serializable {
     private Long id = null;
     private int version;
     private String name;
     private Category parentCategory;
     private Set childCategories = new HashSet();
     private Date created = new Date();
}Categories and Subcategories are implemented in just one class.
But i was thinking in using two classes instead of one, Category and Subcategory. Something like this:
import java.io.Serializable;
public class Category implements Serializable {
     private int id = 0;
     private String title = null;
     private String description = null;
     private List<SubCategory> subCategories = new ArrayList<SubCategory>();
}and
import java.io.Serializable;
public class SubCategory implements Serializable {
     private int id = 0;
     private String title = null;
     private String description = null;
}Maybe is a silly question, but i am not sure of which is the best approach. Can someone help me?
Thanks in advance.

Answer 1

Categories and Subcategories are implemented in just one class.That seems right to me, especially since they're trying to illustrate parent/child relationships.
But i was thinking in using two classes instead of one, Category and Subcategory. Something like this:I see NO value in this design. None whatsoever. The attributes are duplicated. What has repeating yourself bought you? It's not clearer. There's no special behavior associated with being a Subcategory that's different from a Category. Wrong in every way, IMO.
Use the approach in the book. The point isn't the OO design, it's learning Hibernate. Go with it until you've mastered Hibernate.
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