RFR: 8315999: Improve Date toString performance [v10]

[温绍锦]

On Wed, 13 Sep 2023 01:15:38 GMT, 温绍锦 <duke at openjdk.org> wrote:

>> improve date toString performance, includes:
>> 
>> java.util.Date.toString
>> java.util.Date.toGMTString
>> java.time.Instant.toString
>> java.time.LocalDate.toString
>> java.time.LocalDateTime.toString
>> java.time.LocalTime.toString
>
> 温绍锦 has updated the pull request incrementally with one additional commit since the last revision:
> 
>   remove DIGITS_K

> Do you have a link to that PR? Is there an RFE filed for it?

@cl4es  Optimization of DateTimeFormatter::format should be another PR, I created a [branche](https://github.com/wenshao/jdk/tree/optim_for_datetime_format) but the work is unfinished.

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PR Comment: https://git.openjdk.org/jdk/pull/15658#issuecomment-1716790719