RFR: 8269130: Replace usages of Collection.toArray() with Collection.toArray(T[]) to avoid redundant array copying

[Andrey Turbanov]

On Tue, 15 Jun 2021 12:06:43 GMT, Michael Bien <github.com+114367+mbien at openjdk.org> wrote:

>> I found few places, where code initially perform `Object[] Colleciton.toArray()` call and then manually copy array into another array with required type.
>> This PR cleanups such places to more shorter call `T[] Collection.toArray(T[])`.
>
> src/java.base/share/classes/java/security/Security.java line 656:
> 
>> 654:             return null;
>> 655: 
>> 656:         return candidates.toArray(new Provider[0]);
> 
> `candidates.toArray(new Provider[candidates.size()]);`
> 
> would use the fast path of the toArray() implementation. Performance probably doesn't matter much in a lot of this cases, but since its only a few characters more, its still worth considering IMO.
> 
> The only places I would leave this out are on the HashTable and on the Vector collections in this PR, since calling one synchronized method is not the same as calling two - concurrency wise.
> 
> (i am no reviewer)

Actually it's not _the fast path_ - see https://shipilev.net/blog/2016/arrays-wisdom-ancients/

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PR: https://git.openjdk.java.net/jdk/pull/4487