java lambda - how to traverse optional list/stream of optionals

Sara Vino :

Having an Optional List of Optional's like:

Optional<List<Optional<String>>> optionalList = Optional.of(
    Arrays.asList(
        Optional.empty(),
        Optional.of("ONE"),
        Optional.of("TWO")));

How to traverse optionalList to print out the string's ONE and TWO ?

What about having an Optional Stream of Optionals?

Optional<Stream<Optional<String>>> optionalStream = Optional.of(
    Stream.of(
        Optional.empty(),
        Optional.of("ONE"),
        Optional.of("TWO")));

Update: Thanks for answers, solution for optionalStream (non nested):

optionalStream
    .orElseGet(Stream::empty)
    .filter(Optional::isPresent)
    .map(Optional::get)
    .forEach(System.out::println);

user7 :

First, check if the Optional is present. If yes, then stream the list and filter the non-empty ones and print each of them.

optionalList.ifPresent(list -> list.stream()
            .filter(Optional::isPresent)
            .map(Optional::get)
            .forEach(System.out::println));

Almost similar for the stream case too

optionalStream.ifPresent(stream -> stream
            .filter(Optional::isPresent)
            .map(Optional::get)
            .forEach(System.out::println));