신규 아이디 추천

class Solution {
    public String solution(String new_id) {
        String answer = "";
        
        new_id = new_id.toLowerCase();
 
        new_id = new_id.replaceAll("[\\~\\!\\@\\#\\$\\%\\^\\&\\*\\(\\)\\=\\+\\[\\{\\]\\}\\:\\?\\,\\<\\>\\/]", "");
 
        new_id = new_id.replaceAll("[.]+", ".");
 
        new_id = new_id.replaceAll("^[.]|[.]$", "");        
 
        if (new_id.length() == 0)
            new_id = "a";
 
        if (new_id.length() >= 16) {
            new_id = new_id.substring(0, 15);
            if (new_id.substring(14).equals("."))
                new_id = new_id.substring(0, 14);
        }
 
        if (new_id.length() <= 2) {
            int start = new_id.length();
            for (int i = start; i < 3; i++)
                new_id = new_id + new_id.substring(start - 1, start);
        }
 
        answer = new_id;
        
        return answer;
    }
}

특수문자 정규 표현식을 처리하는데 유의해야 한다.