[PATCH] Simplification of TreeMap

[Remi Forax]

Hi Sergey,
if think the code is as it is because it's faster to check for the null comparator and have an ad-hoc code for this special case than using Comparator.naturalOrder(),
obviously, it's not may be true anymore, so you should test that there is no perf regression when creating your patch.

regards,
Rémi

----- Mail original -----
> De: "Сергей Цыпанов" <sergei.tsypanov at yandex.ru>
> À: "core-libs-dev" <core-libs-dev at openjdk.java.net>
> Envoyé: Mardi 4 Septembre 2018 21:14:21
> Objet: [PATCH] Simplification of TreeMap

> Hi,
> 
> currently (latest code of JDK 11) an instance of TreeMap created with no-arg
> contructor has nullable comparator i.e. utilizes no comparator.
> 
> As it comes from the code, a TreeMap created with nullable comparator works
> exactly as a TreeMap created with comparator provided by
> Comparator.naturalOrder(). This is also explicitly specifid in Javadoc.
> 
> I propose to initialize default comparator of TreeMap with instance of
> Comparator returned by Comparator.naturalOrder() instead of null.
> This allows to remove the code responsible for handling nullable comparator, e.
> g. TreeMap::getEntryUsingComparator can be completely removed in favour of
> TreeMap::getEntry.
> Similar simplification available for TreeMap::put, TreeMap::compare,
> EntrySpliterator::getComparator.
> 
> I've prepared a patch for this.
> The patch contains both described major change and some tiny clean-ups e. g.
> utilization of Objects::requireNonNull where appropriate and Objects::equals
> instead of hand-written TreeMap::valEquals.
> 
> TreeMapTest is green after my changes.
> 
> Regards,
> Sergey Tsypanov