class Strings {

    public static String substringAfterLast(String str, String separator) {
        if (isNullOrEmpty(str)) {
            return str;
        }
        if (isNullOrEmpty(separator)) {
            return EMPTY;
        }
        int pos = str.lastIndexOf(separator);
        if (pos == INDEX_NOT_FOUND || pos == str.length() - separator.length()) {
            return EMPTY;
        }
        return str.substring(pos + separator.length());
    }

    private  Strings();

}