[OCAJP]字串陣列

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();
        }
    }
}

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?

97 98
99 100 null null null

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。

MagicLen

[OCAJP]字串陣列

題解

關於作者

Magic Len

相關文章

[LPIC-1]Administrative Tasks 10

[OCPJP]集合與串流

[OCPJP]Path的用法

[OCAJP][OCPJP]程式區塊

[LPIC-1]Scripting and Data Management 10

[LPIC-1]Linux Filesystems 9

[OCAJP]如何印出COJ？

MagicURLNetwork─讓Java使用URL透過網路上傳與下載資料