class DayClustering {

    @Override
    public String toString() {
        if (Arrays.equals(groups, TD7_IDX)) {
            return "TD7";
        }
        if (Arrays.equals(groups, TD2_IDX)) {
            return "TD2";
        }
        if (Arrays.equals(groups, TD3_IDX)) {
            return "TD3";
        }
        if (Arrays.equals(groups, TD3C_IDX)) {
            return "TD3c";
        }
        if (Arrays.equals(groups, TD4_IDX)) {
            return "TD4";
        }
        StringBuilder builder = new StringBuilder();
        int ng = getGroupsCount();
        for (int i = 0; i < ng; ++i) {
            builder.append('{').append(toString(i)).append('}');
        }
        return builder.toString();
    }

      DayClustering(final int[] groups);

}