On Mon, 24 Nov 2025 08:02:35 GMT, Shaojin Wen <[email protected]> wrote:
> This PR optimizes the parsing performance of DateTimeFormatter by replacing
> HashMap with EnumMap in scenarios where the keys are exclusively ChronoField
> enum values.
>
> When parsing date/time strings, DateTimeFormatter creates HashMaps to store
> intermediate parsed values. HashMap has more overhead for operations compared
> to specialized map implementations.
>
> Since ChronoField is an enum and all keys in these maps are ChronoField
> instances, we can use EnumMap instead, which provides better performance for
> enum keys due to its optimized internal structure.
>
> Parsing scenarios show improvements from 12% to 95%
Changes requested by liach (Reviewer).
src/java.base/share/classes/java/time/format/DateTimeFormatterBuilder.java line
2593:
> 2591: for (DateTimePrinterParser pp : printerParsers) {
> 2592: if ((pp instanceof NumberPrinterParser npp &&
> !(npp.field instanceof ChronoField))
> 2593: || (pp instanceof CompositePrinterParser cpp &&
> !cpp.onlyChronoField())) {
Missing check for `TextPrinterParser`
src/java.base/share/classes/java/time/format/Parsed.java line 134:
> 132: if (onlyChronoField) {
> 133: return new HashMap<>();
> 134: } else {
Is this condition inverted :thinking: seems like it but how do you get the
performance numbers
-------------
PR Review: https://git.openjdk.org/jdk/pull/28471#pullrequestreview-3502735627
PR Review Comment: https://git.openjdk.org/jdk/pull/28471#discussion_r2558118611
PR Review Comment: https://git.openjdk.org/jdk/pull/28471#discussion_r2558120676
