@SuppressWarnings("unchecked")
    public static <T> Stream<List<T>> of(final Collection<T> items) {
        return of((T[]) items.toArray());
    }
Creates and returns all possible combinations of the given elements.

The order of the combinations in the stream is unspecified.

@param <T> element type
@param items to combine
@return all possible combinations of the given elements
common-parent/combinatorics/src/main/java/com/speedment/common/combinatorics/internal/CombinationUtil.java