23. 가운데 글자 가져오기 (substring())

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