方法不會從超類型錯誤中覆蓋或實現方法

Question

我正在嘗試為我的國際象棋游戲設計一種撤消/重做機制。.我決定使用將在ArrayList上構建的堆棧數據結構。.我也希望我的UndoStack和RedoStack類應該是單例。越來越

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

錯誤..

這是我的IStackable接口：

package cgas5;


public interface IStackable {

    abstract public Move pop();

    abstract public void push(Move m);

}

和我的UndoStack類

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);
    }
}

並且如果需要我的Move類：

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;
    }

}

提前致謝..

Answer 1

這就是問題：

public class UndoStack<Move> extends ArrayList<Move> 

那是使用Move作為泛型類型參數 ，而實際上您根本不需要泛型-您只想使用Move作為ArrayList<E>的類型參數 。 你要：

public class UndoStack extends ArrayList<Move> 

那應該可以解決問題-盡管我個人強烈建議在這里使用組合而不是繼承。 （換句話說，讓您的UndoStack類型包含 ArrayList<Move> -或類似的名稱-而不是對其進行子類化。）

此外，這永遠行不通：

UndoStack undoStack;

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

這意味着要創建一個UndoStack ，您需要創建另一個UndoStack ……您希望這種情況如何發生？ 當前，您將獲得一個堆棧溢出異常...為什么根本需要該變量？