How should we manage jdk8 stream for null values

Question

Hello fellow Java developers,

I know the subject may be a bit in advance as the JDK8 is not yet released (and not for now anyway..) but I was reading some articles about the Lambda expressions and particularly the part related to the new collection API known as Stream.

Here is the example as given in the Java Magazine article (it is an otter population algorithm..):

Set<Otter> otters = getOtters();
System.out.println(otters.stream()
    .filter(o -> !o.isWild())
    .map(o -> o.getKeeper())
    .filter(k -> k.isFemale())
    .into(new ArrayList<>())
    .size());

My question is what happen if in the middle of the Set internal iteration, one of the otter is null?

I would expect a NullPointerException to be thrown but maybe am I still stuck in the previous development paradigm (non-functional), can someone enlighten me as how this should be handled?

If this really throw a NullPointerException, I find the feature quite dangerous and will have to be used only as below:

• Developer to ensure there is no null value (maybe using a previous .filter(o -> o != null))
• Developer to ensure the application is never generating null otter or a special NullOtter object to deal with.

What is the best option, or any other option?

Thanks!

Answer 1

Although the answers are 100% correct, a small suggestion to improve null case handling of the list itself with Optional:

 List<String> listOfStuffFiltered = Optional.ofNullable(listOfStuff)
                .orElseGet(Collections::emptyList)
                .stream()
                .filter(Objects::nonNull)
                .collect(Collectors.toList());

The part Optional.ofNullable(listOfStuff).orElseGet(Collections::emptyList) will allow you to handle nicely the case when listOfStuff is null and return an emptyList instead of failing with NullPointerException.