Given:



public class Test {

    public static void main(String[] args) {
        String[][] chs = new String[2][];
        chs[0] = new String[2];
        chs[1] = new String[5];
        int i = 97;

        for (int a = 0; a < chs.length; a++) {
            for (int b = 0; b < chs.length; b++) {
                chs[a][b] = "" + i;
                i++;
            }
        }

        for (String[] ca : chs) {
            for (String c : ca) {
                System.out.print(c + " ");
            }
            System.out.println();
        }
    }
}

What is the result?

A.

97 98
99 100 null null null

B.

91 98
99 100 101 102 103

C. Compilation fails.
D. A NullPointerException is thrown at runtime.
E. An ArraylndexOutOfBoundsException is thrown at runtime.

題解

第10行的for迴圈一開始，a = 0, b = 0，所以chs[0][0] = "97"。

接下來，a = 0, b = 1，所以chs[0][1] = "98"。
然後，a = 1, b = 0，所以chs[1][0] = "99"。
最後，a = 1, b = 1，所以chs[1][1] = "100"，跳出迴圈。

其他沒設定到的陣列元素，初始值為null。