Question

Im creating a simple bowling game using OOP, and i want to have a class for each bowl, a Frame class consisting of two bowls, and a Game class consisting of ten frames.

At the moment i have something like this

Bowl.java

public class Bowl {

int bowlScore = 0;

public Bowl(int pinsKnocked){
    bowlScore = pinsKnocked;
}
}

Frame.java

public class Frame{

int firstScore;
int secondScore;
public Bowl firstBowl;
public Bowl secondBowl;

public Frame (){
    firstBowl = new Bowl(0);
    secondBowl = new Bowl(0);
}

public Frame (int firstScore, int secondScore){
    firstBowl = new Bowl(firstScore);
    secondBowl = new Bowl(secondScore);
} 

Game.java

public class Game {

int totalScore;
public Frame firstFrame;
public Frame secondFrame;
...
    public Frame tenthFrame;

public Game(){
    firstFrame = new Frame();   
}

public Game(Frame f){
    firstFrame = f;
}

Is this the correct way of using OOP features or how would I be able to improve this?

Answer 1

There is not a 100% correct way for designing a Bowling game; there are many solutions which will work, and even more that won’t work.

What you need is a solution that will work well for your, and your goals.

If you want to display a score, then I suggest you start with a getScore() method. If you want to display the Winners, start with a displayWinners() method.

Eventually you will find that these methods naturally bind to various nouns. For example, you might start off with getScore() being attached to a Game object, but then realize that this unnaturally means your game can only have one score. If this occurs, you would then move the getScore() to a Player object, and have the game maintain one or more players.

If you are working with a method that naturally belongs somewhere else, there are a number of hints in your code that will guide you. The most obvious hint is that a method seems to be particularly interested in another object’s data, even over it’s own data. In the above example, a getScore() in a game object is overly interested in a Player’s frames, balls, etc.

To gain skills and direction in how to safely move code from one place to another, I recommend reading Martin Fowler’s Refactoring Book.

An excellent example, using exactly your problem is demonstrated here.

Good luck, and after a while you will be able to skip some of this process due to acquired skill; however, when learning for the first time, it is a good idea to not skip such exploratory steps (start at the beginning).

PS. Remember that your code will only be certain to do what you test it to do, if you are not familiar with test driven development, it might be a good idea to look into it (hint, this is a massive understatement).