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From Valerio Schiavoni <>
Subject Re: [all] Null vs. Empty Lists
Date Wed, 11 Jan 2006 20:19:10 GMT
i also suggest to take a look at the Null Object design patter, as it
addresses exactly this issue.
you can google for it, or just follow this link:

2006/1/11, Josh Foure <>:
> Hi all,
> I have noticed that a lot of the commons libraries
> return empty Lists instead of null when a method is
> declared to return a List and  there are no results.
> I have also noticed this in other libraries such as
> Xerces and Xalan.  Is there a best practice concerning
> when to return null and when to return an empty List?
> I see advantages to returning the empty List in that
> you can can always get the iterator without checking
> for null (and iterate through 0 elements when the List
> is empty) or use addAll() on another List without
> first checking for null.  By removing all the null
> checks it seems to make the code cleaner.  However,
> returning null may be a little more consistent in that
> most methods that return a single result object tend
> to return null if the object was not retrieved so why
> would a collection be any different?
> I would love to hear your thoughts on this.
> Thanks,
> Josh
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To Iterate is Human, to Recurse, Divine
James O. Coplien, Bell Labs

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