Question

所以我需要在这段代码中有一个继承的例子，我试图得到它，所以我在父类中实例化private BufferedImage image，然后让它在子类中采用不同的形式，如玩家，敌人，可能还有钥匙。他们每个人都有自己的特定形象（这也是多态性的一个很好的例子吗？）。这是代码：

public class Entity { //hold things such as player, and values realted to that specific entity (nice especially for organization purposes)
Image i = new Image();
MazeModel model = new MazeModel();

private BufferedImage image; //they all have images
}

class Player extends Entity{
image = i.getPlayer();

public void setPlayerStart(){
    model.setPlayerX(50); //sets the starting x position of the player's image
    model.setPlayerY(50); //sets the starting y position of the player's image
}
}
//these next two I will possibly add later if I have the time
class Enemy extends Entity{
//nothing here for now
}

class Key extends Entity{
//nothing here for now
}

Answer 1

private类的实例不能从父类继承到子类，也不能在子类中访问。

因此private BufferedImage image;课程的Entity Player private BufferedImage image;课程无法在protected BufferedImage image;课程中显示。

建议：尝试将此Player设为function array_rekey($a, $column) { $array = array(); foreach($a as $keys) $array[$keys[$column]] = $keys; return $array; }，以便您也可以访问您的孩子（Sub ColumnCheck() Dim i, LastRow, LastRowA, LastRowB, response 'get last row in column A and B, rather than 'iterating through all possible rows LastRowA = Range("A" & Rows.Count).End(xlUp).Row LastRowB = Range("A" & Rows.Count).End(xlUp).Row 'get the greatest row between A and B If LastRowA >= LastRowB Then LastRow = LastRowA Else LastRow = LastRowB End If 'iterate through all rows comparing them. For i = 1 To LastRow If Cells(i, "A").Value <> Cells(i, "B").Value Then response = "The columns are not equal!" Range("E1") = response MsgBox (response) Exit Sub End If Next response = "The columns are equal!" Range("E1") = response MsgBox (response)）课程，并且您的实例变量也是安全的。

Answer 2

将私人更改为公开。

public BufferedImage image;

Answer 3

我会使用getter和setter来使其可访问。

对于您的情况，您可以将每个内部值设为私有，并通过getter和setter访问它：

public class Entity {
    private Image i;
    private MazeModel model;
    private BufferedImage image;

    // initialize these values when calling new
    public Entity() {
        this.i = new Image();
        this.model = new MazeModel();
    }

    // create getter and setter
    public BufferedImage getImage(){
        return this.image;
    }

    public void setImage(BufferedImage image){
        this.image = image;
    }

    public Image getI(){
        return this.i;
    }

    // other code...
}

class Player extends Entity {
    public Player(){
        this.setImage(getI().getPlayer());
    }

    //other code...
}

除了getter和setter之外，您还需要创建Constructor（public Entity（）和public Player（））来初始化值。

无法使用父类中的变量？

3 个答案: