I have 3 Optionals:
Optional<T> optA = getOptA();
Optional<T> optB = getOptB();
Optional<T> optC = getOptC();
Is there a better way to concat them to a Stream<T> than:
Stream.concat(Stream.concat(optA.stream(), optB.stream()), optC.stream());
If the number of optionals grows, this gets unwieldy very soon:
Stream.concat(Stream.concat(optA.stream(), optB.stream()), Stream.concat(optC.stream(), optD.stream());
What about using Stream::of and concat in using reduce:
Stream.of(optA.stream(), optB.stream(), optC.stream(), optD.stream())
.reduce(Stream::concat)
.orElseGet(Stream::empty);
Or you can use a map, and your code should be:
Stream.of(optA, optB, optC, optD)
.map(Optional::stream)
.reduce(Stream::concat)
.orElseGet(Stream::empty);
Which lead you to combine map and reduce using only flatMap as mentioned in comments:
Stream.of(optA, optB, optC)
.flatMap(Optional::stream);