Can I create a non-abstract method in an interface that will be called by every implementation?

Question

I know that interfaces have abstract methods that are inherited by their implementations. I'm wondering if there is a way that I can declare a more concrete method that each implementation will have, and will act in exactly the same way for each implementation.

I have a chess piece interface as a blueprint for creating different pieces, and I want to add each newly instantiated piece to an ArrayList, no matter the specific implementation.

Here is my Piece interface:

public interface Piece {

    public enum Side {
        BLACK, WHITE
    }

    public void getSide();

    public void movePiece(Position position);

    public void takePiece(Position position);

    public void getPosition();
}

And here is my Board class, which contains a list of active pieces which I want to add each piece to when it is created.

import java.util.ArrayList;

public class Board {

    public ArrayList<Piece> activePieces;

}

Do I have to add a specific method to each implementation of Piece? Or is there some way I can include this in the interface? I feel like it's the former, but it just feels like there should be a neater way to do this.

Why not simply use an abstract class if you want this type of behavior? That's what it's for. — Hovercraft Full Of Eels, Sep 21 '17 at 19:16
no method definitions in interfaces. As Hovercraft suggested, use abstract class instead — digidude, Sep 21 '17 at 19:20
@digidude: not entirely true with Java 8, but not recommended in this situation. — Hovercraft Full Of Eels, Sep 21 '17 at 19:22
@HovercraftFullOfEels Agreed. my bad! 'default' method in Java 8 interfaces would fit this questions requirement too. Thanks for pointing that out. — digidude, Sep 21 '17 at 19:24
@digidude: but this is not recommended. The entire purpose of default methods is to add functionality to older interfaces without breaking binary, and so in this situation where the type is an entirely new one, the answer is to use an abstract class. — Hovercraft Full Of Eels, Sep 21 '17 at 19:30

Can I create a non-abstract method in an interface that will be called by every implementation?

0 Answers0