RFR: 8293630: Simplify TreeMap.get() with Comparator.naturalOrder() [v4]

[liach]

On Mon, 17 Oct 2022 10:19:26 GMT, Сергей Цыпанов <duke at openjdk.org> wrote:

>> We can use `Comparator.naturalOrder()` for cases when a `TreeMap` instance is constructed without comparator. This allows to squash two branches in `TreeMap.get()` into one.
>> 
>> P.S. I think the comment of `TreeMap.getEntryUsingComparator()` is outdated. Should we also change it?
>
> Сергей Цыпанов has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8293630: Inline natural()

src/java.base/share/classes/java/util/TreeMap.java line 3329:

> 3327:             }
> 3328:             else {
> 3329:                 return (Comparator<Map.Entry<K, V>> & Serializable) (e1, e2) -> {

I think this cast hints compiler to bootstrap lambda meta factory with extra Serializable marker interface. Meanwhile, Comparator.naturalOrder does not implement Serializable.

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PR: https://git.openjdk.org/jdk/pull/9901