The min non-null LocalDateTime of a list using stream

Question

I know how to get the min LocalDateTime of a list thanks to: https://stackoverflow.com/a/20996009/270143

e.g. LocalDateTime minLdt = list.stream().map(u -> u.getMyLocalDateTime()).min(LocalDateTime::compareTo).get();

My problem is slightly different though...

1. I would like the min LocalDateTime that is not null
2. or null if they are all null

How would I go about doing that in a concise way?

Answer 1

You could simply do:

Optional<LocalDateTime> op = list.stream()
        .filter(Objects::nonNull)
        .min(Comparator.naturalOrder());

And the absent value would indicate that there are only nulls in your List (or your List is empty)