RFR: 8366224: Introduce DecimalDigits.appendPair for efficient two-digit formatting and refactor DateTimeHelper [v13]

[Shaojin Wen]

On Tue, 4 Nov 2025 13:21:06 GMT, Shaojin Wen <swen at openjdk.org> wrote:

>> This PR introduces a new efficient API for appending two-digit integers to StringBuilders and refactors DateTimeHelper to leverage this new functionality.
>> 
>> Changes include:
>> 
>> 1. New `appendPair` method for efficient two-digit integer formatting (00-99):
>>    - Added `AbstractStringBuilder.appendLatin1(char c1, char c2)` with core implementation
>>    - Added `JavaLangAccess.appendPair(StringBuilder, char c1, char c2)` for internal access
>>    - Added `DecimalDigits.appendPair(StringBuilder, int)` public static utility method
>>    - Enhanced Javadoc documentation for all new methods
>> 
>> 2. Refactored `DateTimeHelper` to use the new `DecimalDigits.appendPair`:
>>    - Updated `DateTimeHelper.formatTo` methods for `LocalDate` and `LocalTime`
>>    - Replaced manual formatting logic with the new efficient two-digit appending
>>    - Improved code clarity and consistency in date/time formatting
>> 
>> These changes improve code clarity and performance when formatting two-digit numbers, particularly in date/time formatting scenarios.
>
> Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   remove assert & newCapacity

In the current version, the appendLatin(char c1, char c2) method provided by JavaLangAccess can be used in more scenarios, in addition to date scenarios, it can also be used in other places.

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PR Comment: https://git.openjdk.org/jdk/pull/26911#issuecomment-3509058184