Inflearn Community Q&A

 public static void main(String[] args) throws IOException {
//        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        Scanner br = new Scanner(System.in);
        String line1 = br.nextLine();
        String line2 = br.next();

        System.out.print(findAlphabet(line1, line2));
    }

    public static int findAlphabet(String line1, String line2){
        char[] chars = line1.toCharArray();
        char specialChar = line2.charAt(0);
        int count = 0;
        for (char aChar : chars) {
            if(Character.isUpperCase(aChar)){
                aChar = Character.toLowerCase(aChar);
            }

            if(aChar == specialChar){
                count++;
            }
        }

        return count;
    }