[프로그래머스/자바] 신규 아이디 추천

class Solution {
    public String solution(String new_id) {
        new_id = new_id.toLowerCase();
        
        new_id = new_id.replaceAll("[^0-9a-z\\-_.]", "");
        
        new_id = new_id.replaceAll("\\.+", ".");
        
        new_id = new_id.replaceAll("^\\.+|\\.+$", "");
        
        if (new_id.isEmpty()) new_id = "a";
        
        if (new_id.length() >= 16) new_id = new_id.substring(0, 15);
        new_id = new_id.replaceAll("\\.+$", "");
        
        while (new_id.length() < 3) {
            new_id += new_id.charAt(new_id.length() - 1);
        }
        
        return new_id;
    }
}