RFR: 8356995: Provide default methods min(T, T) and max(T, T) in Comparator interface [v7]

[Chen Liang]

On Fri, 19 Sep 2025 02:25:50 GMT, Stuart Marks <smarks at openjdk.org> wrote:

>> src/java.base/share/classes/java/util/Comparator.java line 201:
>> 
>>> 199:      * @param   o1   an argument.
>>> 200:      * @param   o2   another argument.
>>> 201:      * @param   <U> the type of the arguments and the result.
>> 
>> Since we are utilizing the least upper bound here, we can probably describe this as:
>> 
>> "captures the least upper bound of argument types for the result type"
>> 
>> Or should we leave an API note?
>
> Most docs for type arguments aren't that specific. I checked a bunch in Collections, Collection, and Class, and they're pretty simple and not precise. For example, in Collection we have:
> 
>     <T> T[] toArray(T[] a)
> 
>     @param <T> the component type of the array to contain the collection
> 
> Additionally, I'm not sure that `U` is actually the LUB of the types of the arguments. `U`'s upper bound of `T` might require it to be something different.

I think we still should describe U as only the type of result - the arguments can be more specific, U is any common supertype of the two argument types but is usually induced by Java language rule to be the lub

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PR Review Comment: https://git.openjdk.org/jdk/pull/25297#discussion_r2361583444