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 str = in.nextLine();
        String c = in.nextLine();
        int res = countCharFreq(str, c);
        System.out.println(res);
    }

    public static int countCharFreq(String str, String c){
        if(str == null || str.length()==0 || c == null){
            return 0;
        }
        char[] chars = str.toCharArray();
        int num = 0;
        for(int i = 0;i<chars.length;i++){
            if(c.equalsIgnoreCase(String.valueOf(chars[i]))){
                num++;
            }
        }
        return num;
    }
}