题解 | #计算某字符出现次数#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        String line = in.nextLine();
        char ch = in.nextLine().charAt(0);
        //char cIgnoreCase = ch < 'a' ? (char) (ch + ('a' - 'A')) : ch;
        line = 'a' <= ch && ch <= 'z' ? line.toLowerCase() : ('A' <= ch && ch <= 'Z' ? line.toUpperCase() : line);
        long count = line.chars().filter(e -> e == ch).count();
        System.out.println(count);
    }
}