RFR: 8337168: Optimize LocalDateTime.toString [v3]

[Chen Liang]

On Thu, 25 Jul 2024 22:51:09 GMT, Shaojin Wen <duke at openjdk.org> wrote:

>> The current LocalDateTime.toString implementation concatenates the toString results of date and time, which can be passed to StringBuilder to reduce additional object allocation and improve performance.
>
> Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   change description

src/java.base/share/classes/java/time/LocalTime.java line 1641:

> 1639:     /**
> 1640:      * Prints the toString result to the given buf, avoiding extra string allocations.
> 1641:      * Requires extra capacity of 10 to avoid StringBuilder reallocation.

Suggestion:

     * Requires extra capacity of 18 to avoid StringBuilder reallocation.

Sorry I left a typo, you see toString is `new StringBuilder(18)`

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PR Review Comment: https://git.openjdk.org/jdk/pull/20321#discussion_r1692240103