Java课后题第十二章：12.30（字母出现的次数）

目录

1、创建两个数组（储存A-z的字符及出现次数）

2、二分法遍历并计数

3、示例

        char[] list = new char[52];
        for (int i = 0; i < list.length; i++) {
            if (i < 26)
                list[i] = (char) ('A' + i);
            else
                list[i] = (char) (list[i - 26] + 32);
        }
        int[] list2 = new int[52];

2、二分法遍历并计数

        if (('A' <= s1.charAt(i) && s1.charAt(i) <= 'Z') ||
            ('a' <= s1.charAt(i) && s1.charAt(i) <= 'z'))
        {
            int k = Arrays.binarySearch(list, s1.charAt(i));
            list2[k] = list2[k] + 1;
        }

3、示例

public class CharacterTimes {
    public static void main(String[] args) throws Exception {
        char[] list = new char[52];
        for (int i = 0; i < list.length; i++) {
            if (i < 26)
                list[i] = (char) ('A' + i);
            else
                list[i] = (char) (list[i - 26] + 32);
        }
        int[] list2 = new int[52];

        File file = new File("Text.txt"); // 先建立文件
        Scanner input = new Scanner(file);
        while (input.hasNext()) {
            String s1 = input.nextLine();
            for (int i = 0; i < s1.length(); i++)
                if (('A' <= s1.charAt(i) && s1.charAt(i) <= 'Z') ||
                        ('a' <= s1.charAt(i) && s1.charAt(i) <= 'z'))
                {
                    int k = Arrays.binarySearch(list, s1.charAt(i));
                    list2[k] = list2[k] + 1;
                }
        }
        input.close();
        for (int i = 0; i < 52; i++) {
            System.out.print("Number of " + list[i] + "'s:" + list2[i]+"  ");
            if (i % 9 == 8)
                System.out.println();
        }
    }
}

Number of A's:0  Number of B's:1  Number of C's:0  Number of D's:1  Number of E's:0  Number of F's:0  Number of G's:0  
Number of H's:0  Number of I's:1  Number of J's:0  Number of K's:0  Number of L's:0  Number of M's:0  Number of N's:0  
Number of O's:0  Number of P's:0  Number of Q's:0  Number of R's:0  Number of S's:0  Number of T's:0  Number of U's:0  
Number of V's:0  Number of W's:1  Number of X's:0  Number of Y's:0  Number of Z's:0  Number of a's:20  Number of b's:1  
Number of c's:3  Number of d's:8  Number of e's:28  Number of f's:8  Number of g's:6  Number of h's:12  Number of i's:11  
Number of j's:0  Number of k's:4  Number of l's:4  Number of m's:6  Number of n's:22  Number of o's:22  Number of p's:3  
Number of q's:0  Number of r's:16  Number of s's:17  Number of t's:29  Number of u's:10  Number of v's:1  Number of w's:9  
Number of x's:0  Number of y's:6  Number of z's:0