class EmailUtil {

    public static String getResponseSubject(IdentifiableEmailWithSubject emailWithSubject) {
        final String subject = emailWithSubject.getSubject();
        final int length = subject.length();
        if (length <= 3) {
            return subjectWithPrefix(subject);
        }
        final String prefix = subject.substring(0, 3);
        if (prefix.charAt(2) == ':' && RESPONSE_PREFIXES.contains(prefix.substring(0, 2).toLowerCase())) {
            return subjectWithPrefix(subject.substring(3));
        }
        return subjectWithPrefix(subject);
    }

    private  EmailUtil();

}