Question

我正在尝试为我的国际象棋游戏设计撤消/重做机制。我决定使用堆栈数据结构，它将构建在ArrayList上。我还希望我的UndoStack和RedoStack类应该是单例。但是我得到了

method does not override or implement a method from a supertype

pop() in UndoStack cannot implement pop() in IStackable
  return type Move is not compatible with cgas5.Move
  where Move is a type-variable:
    Move extends Object declared in class UndoStack

错误..

这是我的IStackable界面：

package cgas5;


public interface IStackable {

    abstract public Move pop();

    abstract public void push(Move m);

}

和我的UndoStack类

package cgas5;

import java.util.ArrayList;

public class UndoStack<Move> extends ArrayList<Move> implements IStackable {

    UndoStack undoStack;

    private UndoStack() {
        undoStack = new UndoStack();
    }

    public UndoStack getUndoStack() {
        if (undoStack == null) {
            undoStack = new UndoStack();
        }
        return undoStack;
    }

    @Override
    public Move pop() {
        Move m = get(size() - 1);
        remove(size() - 1);
        return m;

    }

    @Override
    public void push(Move m) {
        add(m);
    }
}

如果有必要我的Move类：

package cgas5;

public class Move {
    private Piece pieceToMove;
    private Square currentSquare;
    private Square targetSquare;
    private Piece capturedPiece;
    private Piece promotedPiece;

    public Move(){

    } 

    public Move(Piece pieceToMove, Square currentSquare, Square targetSquare){
        this.pieceToMove = pieceToMove;
        this.currentSquare = currentSquare;
        this.targetSquare = targetSquare;
    }

    public Piece getPieceToMove() {
        return pieceToMove;
    }

    public void setPieceToMove(Piece pieceToMove) {
        this.pieceToMove = pieceToMove;
    }

    public Square getCurrentSquare() {
        return currentSquare;
    }

    public void setCurrentSquare(Square currentSquare) {
        this.currentSquare = currentSquare;
    }

    public Square getTargetSquare() {
        return targetSquare;
    }

    public void setTargetSquare(Square targetSquare) {
        this.targetSquare = targetSquare;
    }

    public Piece getCapturedPiece() {
        return capturedPiece;
    }

    public void setCapturedPiece(Piece capturedPiece) {
        this.capturedPiece = capturedPiece;
    }

    public Piece getPromotedPiece() {
        return promotedPiece;
    }

    public void setPromotedPiece(Piece promotedPiece) {
        this.promotedPiece = promotedPiece;
    }

}

提前致谢..

Answer 1

这是问题所在：

public class UndoStack<Move> extends ArrayList<Move>

那是使用Move作为泛型类型参数，而实际上你根本不需要泛型类型 - 你只想使用Move作为类型< ArrayList<E>的em>参数。你想要：

public class UndoStack extends ArrayList<Move>

这应该可以解决问题 - 虽然我个人强烈建议在这里使用合成而不是继承。（换句话说，让你的UndoStack类型包含一个ArrayList<Move> - 或类似的东西 - 而不是继承它。）

此外，这永远不会起作用：

UndoStack undoStack;

private UndoStack() {
    undoStack = new UndoStack();
}

这意味着要创建UndoStack，您需要创建另一个UndoStack ...您希望如何发生这种情况？你现在会得到一个堆栈溢出异常......为什么你需要变量呢？

方法不会覆盖或实现超类型错误的方法

1 个答案: