가운데 글자 가져오기

class Solution {
    public String solution(String s) {
        String answer = "";
        int len = s.length(), mid = len / 2;
        if (len % 2 == 0)
            answer = s.substring(mid - 1, mid + 1);
        else
            answer = s.substring(mid, mid + 1);
        return answer;
    }
}