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https://issues.apache.org/jira/browse/COLLECTIONS-276?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12541703
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Simon Kitching commented on COLLECTIONS-276:
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It's a proposal worth thinking about, but I'm in favour of leaving out the
final and private constructor.
One good reason to allow instances of util types is that certain tools cannot
handle static methods. For example, the JSP EL expression language always
requires a bean instance; it might be useful to configure a utils object as a
"managed bean" in a JSF app for example, but this only works if there is a
constructor available. Not sure if this applies to Collection util classes, but
it certainly does to BeanUtils utility classes etc.
And this warning is only a recommended coding convention. Not everyone will
want to stick with it. If someone does want to subclass, then they can always
use the @SuppressWarnings annotation to suppress this for the appropriate
methods rather than write dummy methods.
As Stephen says, I think there would need to be a specific advantage before
user choice is removed. I guess there is a performance benefit to having a
final class, but I'm not sure this is really significant.
> *Utils classes should not be extensible or able to be instantiated.
> -------------------------------------------------------------------
>
> Key: COLLECTIONS-276
> URL: https://issues.apache.org/jira/browse/COLLECTIONS-276
> Project: Commons Collections
> Issue Type: Improvement
> Affects Versions: Generics
> Reporter: Stephen Kestle
> Priority: Minor
> Fix For: Generics
>
>
> I don't see any good reason why this CollectionUtils (and others) isn't final
> with a private constructor. There are no non-static methods, and any
> extension of them is going to have to call through to the super to avoid
> compiler warnings.
> e.g. MyCollectionUtils.select() will provoke the warning that "static methods
> should be called directly" (on CollectionUtils).
> Which would mean
> MyCollectionUtils{
> public static Collection select(){
> return CollectionUtils.select();
> }
> Which really defeats the purpose. In Java5, we have static imports now -
> these provide more benefit than previous extension did anyhow.
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