929. 独特的电子邮件地址

  HashSet<String> set = new HashSet<>();
        for (String email : emails) {
            int index = email.indexOf("@");
            //姓名
            StringBuilder name = new StringBuilder();
            for (int i = 0; i < index; i++) {
                if (email.charAt(i) == '+') break;
                else if(email.charAt(i)=='.') continue;
                name.append(email.charAt(i));
            }
            //域名
            String domain = email.substring(index + 1);
            set.add(name.append("@").append(domain).toString());
        }
        return set.size();