Get field of optional object or return null

问题

I have optional object:

Optional<Detail> newestDetail;

I would like to return newestDetail.getId() or if newestDetail is null return null.

Do we have more sophisticated approach of doing this, than following?

return newestDetail.isPresent()?newestDetail.get().getId():null;

回答1:

Map the value to an Optional with the id field and turn that one into a null value if it is empty:

return newestDetail.map(Detail::getId).orElse(null);

来源：https://stackoverflow.com/questions/47714105/get-field-of-optional-object-or-return-null