获取indexOutOfBOundException 0

Question

为什么我在下一行继续获得indexOutOfBOundException 0？：

rotatedShape[r][c] = shape[c][height-1-r]; 

方法rotateCW()顺时针旋转char[][] 90度，但我不断收到错误。请问smb请看一下？谢谢！

public static void main(String[] args)
{
    CreateShape temp = new CreateShape(10,10, 'a', 
        new char[][]{{'x','.','.'}, 
                     {'.','.','x'}, 
                     {'x','.','x'}}, 
        "x . .\n"
        + ". . x\n"
        + "x . x");   
    temp.rotateCW();
    System.out.println(temp);
}

public class CreateShape implements Shape {

    private String tempLayout  = "";
    private String layout;
    private int height;
    private int width;
    private char dc;
    private Rotation initialPos;
    private Rotation nextPos;
    private char[][] shape; 
    private char[][] rotatedShape = new char[height][width];// = new char[shape.length][shape[0].length];


    public CreateShape(int height, int width, char dc, char[][] charLayout, String layout)
    {
        this.height = height;
        this.width = width;
        this.dc = dc;
        this.shape = charLayout;
        this.layout = layout;
        initialPos = Rotation.CW0;
    }

    public void rotateCW() 
    {
    //  String tempLayout = "";
        nextPos = initialPos.next();

        /*for(int r = 0; r < height; r++)
            for(int c = 0; c < width; c++)
            {
                rotatedShape[c][height-1-r] = shape[r][c];
                layout += rotatedShape[c][height-1-r];
            }*/
        for(int r = 0; r < height; r++)
            for(int c = 0; c < width; c++)
            {
                rotatedShape[r][c] = shape[c][height-1-r];
                tempLayout += rotatedShape[r][c];

            }
    }
}

Answer 1

CreateShape temp = new CreateShape(10,10, 'a', new char[][]{{'x','.','.'}, 
                                                                  {'.','.','x'}, 
                                                                  {'x','.','x'}}, "x . .\n"
                                                                                + ". . x\n"
                                                                                + "x . x");

您传入的宽度和高度为10，但您的数组仅为3x3。然后根据宽度/高度10继续循环遍历3x3数组（shape）。

for(int r = 0; r < height; r++)
        for(int c = 0; c < width; c++)
        {
            rotatedShape[r][c] = shape[c][height-1-r];
            tempLayout += rotatedShape[r][c];

        }
}

10大于3.这显然会导致IndexOutOfBounds例外。

Answer 2

在你知道它的高度和宽度之前，你要实例化你的数组。具体来说，这三个声明正在打破你：

private int height;
private int width;
private char[][] rotatedShape = new char[height][width];

Java在构造时有一个关于未分配变量的特殊规则。如果未分配，they are assigned to an initial value。对于基元和boolean，它分别为0和false;对于对象，它是null。

你在这里所做的是有效地创建一个大小（0,0）的数组，这就是为什么你在任何时候超出界限的索引。

我的直觉告诉我你不需要height或width字段。你要做的是声明rotatedShape - 只是声明它，不要实例化它。

private char[][] rotatedShape;

在构造函数内部，当知道高度和宽度时，然后，然后才能正确实例化数组。

public CreateShape(int height, int width, char dc,
                   char[][] charLayout, String layout) {
    this.dc = dc;
    this.shape = charLayout;
    this.layout = layout;
    initialPos = Rotation.CW0;
    rotatedShape = new char[height][width];
}