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);
        String str=in.nextLine();
        String char1=in.nextLine();
        char char2=char1.charAt(0);
        if(Character.isLetter(char2)){
            int lowerLength=str.replaceAll("["+char1.toLowerCase()+"]","").length();
            int upperLength=str.replaceAll("["+char1.toUpperCase()+"]","").length();
            System.out.println(str.length()*2-lowerLength-upperLength);
        }else{
            int length=str.replaceAll("["+char1+"]","").length();
            System.out.println(str.length()-length);
        }

    }
}