For-each并分配给2d数组Java

Question

我正在使用for-each循环在基本java程序中移动2d字符数组.它起作用,除了最后的一小部分.这是我的班级:

static String letters = "abcdefghijklmnopqrstuvwxyz";

public static boolean checkIsNumeric(String s) {
    boolean haveBeenNonDigitCharacters = false;
    char[] chars = s.toCharArray();
    for(char c : chars)
        if(!Character.isDigit(c)) {
            haveBeenNonDigitCharacters = true;
            break;
        }

    if(haveBeenNonDigitCharacters) 
        return false;
    else 
        return true;
}

public static char[][] createArray() {
    String height;
    String width;
    Scanner s = new Scanner(System.in);
    do {
        System.out.println("How tall do you want the array to be?");
        height = s.next();
    } while(!checkIsNumeric(height));
    do {
        System.out.println("How wide do you want the array to be?");
        width = s.next();
    } while(!checkIsNumeric(width));

    int intHeight = Integer.parseInt(height);
    int intWidth = Integer.parseInt(width);

    char[][] chars = new char[intWidth][intHeight];

    for(char c[] : chars) {
        for(char d : c)
            d = ' ';
    }

    return chars;
}

public static char[][] fillArray(char[][] a) {
    int counter = 0;
    for(char c[] : a) {
        for(char d : c) {
            if(counter >= 26)
                counter = 0;
            d = letters.charAt(counter);
            counter++;
        }
    }
    return a;
}

public static void main(String[] args) {
    char[][] chars = createArray();
    chars = fillArray(chars);

    for(char c[] : chars) {
        for(char d : c) {
            System.out.print(d);
            if(d == ' ')
            System.out.print("a");
        }
        System.out.println("");
    }
}

基本上,我想做的是采用任何具有用户指定尺寸的二维数组,并用字母表中的字母一遍又一遍地填充它,直到它满了.该checkIsNumeric方法只是检查a String是否为数字,该createArray方法使用用户指定的维度创建2d数组,并且该fillArray方法使用字符串中的字母填充数组.但是当我在main的末尾遍历数组并打印每个字符时,没有任何内容被打印出来.为什么？

Answer 1

更改fillArray到:

public static char[][] fillArray(char[][] a) {
    int counter = 0;

    for (int i = 0; i < a.length; i++) {
        for (int j = 0; j < a[i].length; j++) {
            if(counter >= 26)
                counter = 0;
            a[i][j] = letters.charAt(counter);
            counter++;
        }
    }

    return a;
}

这样a就可以修改实际的数组,而不是for-each循环创建的副本.

这将给出输出(我假设是正确的):

How tall do you want the array to be?
5
How wide do you want the array to be?
4
abcde
fghij
klmno
pqrst

createArray如果您希望每个char都初始化为,则同样如此' '.在main,如果你转换d为int并打印它,你会看到每个char都设置为它的初始值0.