* It is usually a combination of a string and a number, with the string first and the number second.
     */
    private static class CombinationItem implements Item {

        StringItem stringPart;

        Item digitPart;

        CombinationItem(String value) {
            int index = 0;
            for (int i = 0; i < value.length(); i++) {
                char c = value.charAt(i);