Krdytkyu

I want to convert my list of optional strings to a list of strings by getting rid of the empty Optionals.

Is there a shorter version for achieving this than the following code (except statically importing the methods of Collectors)?

List<Optional<String>> stringsMaybe = Arrays.asList(Optional.of("Hi"),

                                      Optional.empty(), Optional.of(" there!"));



List<String> strings = stringsMaybe

            .stream()

            .filter(Optional::isPresent)

            .collect(Collectors.mapping(Optional::get, Collectors.toList()));

It's more idiomatic to use .map on the stream instead of Collectors.mapping:

stringsMaybe.stream()

    .filter(Optional::isPresent)

    .map(Optional::get)

    .collect(toList());

Without introducing a helper method or a custom collector, that's the shortest and clearest way to do this.

Optional will get a stream method in java 9, so you will be able to do .flatMap(Optional::stream) instead of .filter(...).map(...).

If you are using rxJava you can do something like:

Flux<Optional<String>> maybeStrings = Flux.just(

    Optional.of("Hi"),

    Optional.empty(),

    Optional.of(" there!"));



Flux<String> strings = maybeStrings.handle((maybeString, synchronousSink) -> 

    maybeString.ifPresent(synchronousSink::next));