Hello Chris
Le 30/03/13 00:35, Mattmann, Chris A (388J) a écrit :
(...snip...)
However DataQuality [1] have another property, "lineage", and ISO 19115
said that those two properties are mutually exclusive. If the "lineage"
property is set, what should getReports() returns?
How about Collections.unmodifiable{List|Map|etc}?
In this context, it would be Collections.empty{Set|List}. The point was
that we could see a nuance between "no elements", and "elements can not
exist here in current context". In the first case, users can add
elements. In the second case, they can not. Returning a null value in
the second case would be a way to differentiate them.
Returning Collections.empty{Set|List} means that it is not worth to
distinguish those two possibilities, which is a perfectly valid decision
for keeping the API simpler. Eventually, the exception thrown by
Collection.add(...) could contains a message saying why elements can't
be added.
Returning null make the job a little bit easier in some situations like
XML marshalling, where empty XML element is not the same than no XML
element. But this can be considered as an implementation details.
Martin
