创建名为 RubikRight 的 Rubik class 的子 class

Question

我有一个 Rubik class 具有以下内容：

public class Rubik{

    private int[][][] grid;
    protected Face[] cube;
    protected Face up;
    protected Face left;
    protected Face front;
    protected Face right;
    protected Face down;
    protected Face back;
    private static String dots = "......";
    private String output;

    //Constructor
    public Rubik(int[][][] grid){
        int[][][] copy_grid = new int[6][3][3];
        for (int k = 0; k < 6; k++){
            for (int i = 0; i < 3; i++){
                for (int j = 0; j < 3; j++)
                copy_grid[k][i][j] = grid[k][i][j];
            }
        }
        this.grid = copy_grid;
        this.up = new Face(grid[0]);
        this.left = new Face(grid[1]);
        this.front = new Face(grid[2]);
        this.right = new Face(grid[3]);
        this.down = new Face(grid[4]);
        this.back = new Face(grid[5]);
        this.cube = new Face[]{this.up, this.left, this.front, this.right, this.down, this.back};
    }

我正在尝试创建一个扩展 Rubik 的 RubikRight class，并且 RubikRight 的定位方式是原始 Rubik 的右面现在朝向前方。这就是我为 RubikRight 定义构造函数的方式：

public class RubikRight extends Rubik{

    //Constructor
    public RubikRight(int[][][] grid){
        int[][][] copy_grid = new int[6][3][3];
        for (int k = 0; k < 6; k++){
            for (int i = 0; i < 3; i++){
                for (int j = 0; j < 3; j++)
                copy_grid[k][i][j] = grid[k][i][j];
            }
        }
        this.grid = copy_grid;
        this.up = new Face(grid[0]);
        this.left = new Face(grid[2]);
        this.front = new Face(grid[3]);
        this.right = new Face(grid[5]);
        this.down = new Face(grid[4]);
        this.back = new Face(grid[1]);
        this.cube = new Face[]{this.up, this.left, this.front, this.right, this.down, this.back};
    }

但是，我收到错误

Constructor Rubik in class Rubik cannot be applied to the given type;
  public RubikRight(int[][][] grid){
                                     ^
  required: int[][][]
  found: no arguments
  reason: actual and formal argument lists differ in length
1 error

我可以知道为什么我似乎不能那样定义 RubikRight 吗？

Answer 1

您没有调用父 class 的构造函数。

你在这里可以做的是，在父 class 中重载构造函数。创建默认构造函数（无参数构造函数）并使其受保护。

public class Rubik{
  ...
  protected Rubik() {
  }
}

这应该可以解决您的问题。

Answer 2

每当您实例化子 class 对象时，都会隐式调用父 class 默认构造函数。因此，当您通过调用 new RubikRight(int[][][]) 实例化 RubikRight 时，它会从 RubikRight 的构造函数内部隐式调用 super()。因此错误：

required: int[][][] // what you have in Rubik class, note that you don't have the default constructor
found: no arguments // super(/* no argument */) called implicitly

要消除错误，您有两种选择：

从 RubikRight 构造函数显式调用 super(grid)。
或者，在 Rubik（基础）class.

创建名为 RubikRight 的 Rubik class 的子 class

Creating a child class of Rubik class called RubikRight

java

rubiks-cube