[Level1/JAVA] 신규 아이디 추천

class Solution {
    public String solution(String new_id) {
        String answer = "";
        new_id = new_id.toLowerCase();
        new_id = new_id.replaceAll("[^0-9a-z-_.]", "");
        new_id = new_id.replaceAll("[.]{2,}", ".");
        new_id = new_id.replaceAll("^[.]|[.]$", "");

        if(new_id.equals("")) {
            new_id += "a";
        }

        if(new_id.length() >= 16) {
            new_id = new_id.substring(0,15);
            new_id = new_id.replaceAll("[.]$", "");
        }
        

        if(new_id.length() < 3) {
            while (new_id.length() < 3) {
                new_id += new_id.charAt(new_id.length()-1);
            }
        }
        
        answer = new_id;
        return answer;
    }
}