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

You can hack your way around. See the following example:

Stream> stream = Stream.of("Cat", "Dog", "Whale", "Mouse")
   .collect(Collectors.collectingAndThen(
       Collectors.partitioningBy(a -> a.length() > 3),
       map -> Stream.of(map.get(true), map.get(false))
    ));