What is the (kind of) inverse operation to Java's Stream.flatMap()?

Question

The Stream.flatMap() operation transforms a stream of

a, b, c

into a stream that contains zero or more elements for each input el

Answer 1

    IntStream.range(0, 10)
            .mapToObj(n -> IntStream.of(n, n / 2, n / 3))
            .reduce(IntStream.empty(), IntStream::concat)
            .forEach(System.out::println);

As you see elements are mapped to Streams too, and then concatenated into one large stream.