Question

I am developing a simple game. I created a Maze class which contains methods and algorithms for creating / modifying / solving mazes. I also created a GraphicalMaze class, which should only contain a paint method to draw the maze on a JPanel.

At this point, i have to decide if:

• GraphicalMaze should extends Maze, with a JPanel as member variable (inheritance)

or

• GraphicalMaze should extends JPanel, with Maze as member variable (composition)

This problem recurs every time i have to create ‘gui’ objects from ‘abstract’ ones.
I am interested in your opinions, and i want to understand what is the ‘right’ way to proceed.

Answer 1

This is not the easiest or most objective question to answer. There are some who tend to say you should favor composition over inheritance in most cases. I would say, think about your objects and how they really relate to each other. In this case, remember that inheritance represents an is-a relationship, whereas composition represents a has-a.

So, the question becomes, is-a GraphicalMaze a Maze? Or is it the representation of a maze? I would argue its the latter. Which of course means you would be using composition instead of Inheritance to represent it.