Question

I am creating a game for my school project, so I am not here for any kind of code, just a global idea on how to do what I am trying to do…

I have Pieces and each piece as is own color and Type like this :
Piece 1 – Yellow – Simple
Piece 2 – Yellow – Explosive
….
Piece 10 – Blue – ChangeColor

At start the game will be field with random pieces from this list (a list created earlier with just one kind of each piece), if we have 3 or more in a row the game as to remove them and count the points, but if one of the 3 (or more) has any “power effect” than the pieces arround must react to that power (hard to explain with my low english level but I think you got it :S..)

For now my game only had simple pieces, and for that I used and enum like this :

public enum CorPeca 
{    
     AMARELO,
     AZUL,
     VERMELHO;
}

On the board class I was doing this :

    this.arrayPecas = new ArrayList<Peca>();

    for (CorPeca corPeca : CorPeca.values())
        this.arrayPecas.add(new Peca(corPeca));

and on the Pieces class i was doing this

public Peca(CorPeca tipoPeca)
{
    this.definirPeca(tipoPeca);
}

public CorPeca getCorPeca() { return this.corPeca; }
public char getCharPeca() { return this.charPeca; }

public void definirPeca(CorPeca tipoPeca)
{
    switch (tipoPeca)
    {
        case AMARELO:
            this.charPeca = 'a';
            this.corPeca = CorPeca.AMARELO;
            break;
        case AZUL:
            this.charPeca = 'u';
            this.corPeca = CorPeca.AZUL;
            break;
        case VERMELHO:
            this.charPeca = 'e';
            this.corPeca = CorPeca.VERMELHO;
            break;                
    }
}

But I was thinking of a good method to easily add those “Power Pieces”, but more than that, being able to add more colors and more “Powers” in the future…

I was thinking about creating subclasses and using extend, but the whole idea just don’t fill in my mind since we can’t extends several classes…

So can anyone give me a global idea on how I can archive that ?

Answer 1

The classic OOP way to do this would be to define an abstract base class that represents all pieces and contains common functionality (such as a list of powers):

public abstract class Piece {
    // put in fields that every piece has, e.g. x and y co-ordinate here

    // array of powers
    protected ArrayList<Power> powers=new ArrayList<Power>();

    // method to add new powers to the piece
    public void addPower(Power power) {
        powers.add(power);
    }

    // power method - optionally overriden by specififc pieces
    public void applyPowers() {
        for (Power power:powers) {
            power.methodToActivatePower();
        }
    }

    // abstract char method
    public abstract char getChar();

}

Note that abstract means that you can’t directly instantiate this class – you can only make instances of concrete subclasses.

Then extend this class to implement each specific piece:

public class YellowPiece extends Piece {

    // override applyPowers for yellow piece (if needed)
    @Override
    public void applyPowers() {
        // code for yellow piece power handling goes here
    }

    // override char - required
    @Override
    public char getChar() {
        return 'y';
    }

}

You can still create an ArrayList<Piece> and populate it with something like:

ArrayList<Piece> pieces = new ArrayList<Piece>();
pieces.add (new YellowPiece());
pieces.add (new GreenPiece());
// etc....

Then if you want to apply the power of a specific piece, just do:

pieces.get(pieceNumber).applyPower();

You’ll obviously need to customise this code a lot to make it work in your game, but hopefully it gives you the general idea. Note that there are lots of other ways of achieving the same goals – I’ve just described the “classic” OOP way.

P.S. Apologies for all code being in English, but your English is far better than my Portugese 🙂