Comments on: Never return Null Arrays!

By: scott

scott — Fri, 17 Oct 2008 17:00:39 +0000

Hi Peter,
It’s a much larger issue to distinguish between java primitive arrays and Java Collection classes, but my advice applies to both WLOG.
Thanks,
-Scott

By: Frank Carver

Frank Carver — Fri, 17 Oct 2008 09:39:36 +0000

It seems this blog does not support trackbacks. For interest I have written a response to this post at:

http://blog.punchbarrel.com/2008/10/16/never-return-null-arrays-really/

By: Peter Lawrey

Peter Lawrey — Fri, 17 Oct 2008 07:00:53 +0000

Someone reading this might be confused about what the difference between Lists and arrays might be. I suggest that your examples should match your text.
Perhaps you could comment that it a good idea not to return null collections or arrays.

By: alepuzio

alepuzio — Thu, 16 Oct 2008 07:35:25 +0000

I agree with you: the null value must mean “error at runtime”, not “empty value”: why don’t use the assertions?

see too http://www.basilv.com/psd/blog/2008/how-to-handle-null-values-in-code

By: oh

oh — Wed, 15 Oct 2008 15:10:14 +0000

Completely agree, never return null instead of an empty collection. In general, require that the client performs null checks on the return value of a function is also a bad idea, usually there are better ways to indicate errors.
The approach you suggest is also recommended in Effective Java by J. Bloch.

By: Casper Bang

Casper Bang — Wed, 15 Oct 2008 14:16:31 +0000

Good advice, seldom followed. We should strive to avoid “if”, as a successor to Dijkstra, “if is evil”. Remember, Collections define EMPTY_LIST, EMPTY_SET and EMPTY_MAP which are very handy in these cases (and reads better than alternatives).

By: Frank Behrens

Frank Behrens — Wed, 15 Oct 2008 11:49:25 +0000

And remember that you can easily return an empy Collection (List, Set, …) with
java.util.Collections.EmptyList (EmptySet, EmptyMap). You don’t have to allocate a new object.