public static List<String> getAlphabetCombination(int order) {
        if (order <0 || order>3) {
            throw new IllegalArgumentException("Supports order 1,2, or 3");
        }
        switch(order) {
            case 1: return ALPHABET_COMBINATIONS_1;
            case 2: return ALPHABET_COMBINATIONS_2;
            case 3: return ALPHABET_COMBINATIONS_3;
        }
        return null;
    }