[jira] [Commented] (LANG-564) Improve StrLookup API documentation

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[jira] [Commented] (LANG-564) Improve StrLookup API documentation

ASF GitHub Bot (Jira)

    [ https://issues.apache.org/jira/browse/LANG-564?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13089035#comment-13089035 ]

Etienne Neveu commented on LANG-564:
------------------------------------

I was also confused by the StrLookup type parameter while browsing the commons-lang 3.0.1 source. Instead of creating a duplicate issue, I thought it would be better to comment here, even though this issue seems to be closed...


I don't see the point of having a generic type parameter on the StrLookup class, if it's not used anywhere. No method / field in StrLookup references this type parameter. IntelliJ IDEA itself reports a warning: "Type parameter 'V' is never used". Moreover, Java generics are not reified, so there is no reliable way to access the type parameter at runtime (and I don't see the point of doing that anyway...).

While the Javadoc tries to clarify the purpose of a StrLookup, the unused type parameter is still confusing, and the client code has to un-necessarily specify type parameters. For example, I have to write:

{code}
StrLookup<?> lookup = StrLookup.noneLookup();
StrLookup<String> lookup2 = StrLookup.systemPropertiesLookup();
StrLookup<Integer> lookup3 = StrLookup.mapLookup(integerMap);
{code}

instead of

{code}
StrLookup lookup = StrLookup.noneLookup();
StrLookup lookup2 = StrLookup.systemPropertiesLookup();
StrLookup lookup3 = StrLookup.mapLookup(integerMap);
{code}


My best guess is that this type parameter was added when commons-lang was generified, because StringLookup.mapLookup() takes a generified Map. Doing this is not really needed, though: we could remove the <V> type parameter everywhere, and replace the StrLookup.mapLookup()'s Map<String, V> with a Map<String, ?> (which is the same as Map<String, ? extends Object>, but shorter).

I guess it's too late to change this now, due to backward compatibility... But I thought I'd comment just in case it's still possible.

> Improve StrLookup API documentation
> -----------------------------------
>
>                 Key: LANG-564
>                 URL: https://issues.apache.org/jira/browse/LANG-564
>             Project: Commons Lang
>          Issue Type: Bug
>          Components: lang.text.*
>            Reporter: Sebb
>             Fix For: 3.0
>
>
> The API for StrLookup is confused. The class has been partly genericised, but why?
> The Javadoc says the class is for looking up Strings which are indexed by Strings, and this agrees with the method lookup()
> Surely if the class is generic on <V>, the lookup() method should return V, not String?
> Does it make any sense for the class to return anything but a String? If not, then why is the class generic?
> If it does make sense, then lookup() should return V.

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