Find all permutations of given items using Java 8

Permutations.java

public class Permutations {

    public static <T> Stream<Stream<T>> of(final List<T> items) {
        return IntStream.range(0, factorial(items.size())).mapToObj(i -> permutation(i, items).stream());
    }

    private static int factorial(final int num) {
        return IntStream.rangeClosed(2, num).reduce(1, (x, y) -> x * y);
    }

    private static <T> List<T> permutation(final int count, final LinkedList<T> input, final List<T> output) {
        if (input.isEmpty()) { return output; }

        final int factorial = factorial(input.size() - 1);
        output.add(input.remove(count / factorial));
        return permutation(count % factorial, input, output);
    }

    private static <T> List<T> permutation(final int count, final List<T> items) {
        return permutation(count, new LinkedList<>(items), new ArrayList<>());
    }

}

Permutations.of(Arrays.asList(1, 2, 3)).forEach(p -> { p.forEach(System.out::print); System.out.print(" "); });

will return:
123 132 213 231 312 321

Hey, can you please tell me which packages I have to include? It does´nt run on my Java.

import java.util.stream.*;