class CollectionHelper {

    @SafeVarargs
    public static <T> Set<T> distinct(Collection<T>... collections) {
        Validate.notNull(collections, "collections must not be null");
        Set<T> distinct = new HashSet<>();
        for (Collection<T> collection : collections) {
            distinct.addAll(collection);
        }
        return distinct;
    }

    private  CollectionHelper();

}