alhudz opened a new pull request, #1800:
URL: https://github.com/apache/commons-lang/pull/1800
`FastDatePrinter.parsePattern` builds the `G` rule from
`DateFormatSymbols.getEras()`, a two-entry Gregorian table, but the printer
formats with `Calendar.getInstance(timeZone, locale)`, which is the Thai
Buddhist calendar for `th_TH` and the Japanese Imperial calendar for
`ja_JP_JP`. The year comes from that calendar and the era label from the
Gregorian table, so `FastDateFormat.getInstance("G yyyy", th_TH)` prints `ค.ศ.
2567` (AD 2567) where `SimpleDateFormat` prints `พ.ศ. 2567`, and
`parse(format(date))` then throws `ParseException` because `FastDateParser`
takes its era names from the calendar. For `ja_JP_JP` the Reiwa era value is 5,
so `format` throws `ArrayIndexOutOfBoundsException` from `TextField.appendTo`.
Take the era names from the printer's own calendar when its type is not
`gregory`, sized to `Calendar.getMaximum(ERA)` and using the long names for
`GGGG` as `SimpleDateFormat` does; Gregorian locales keep
`DateFormatSymbols.getEras()` so their output is unchanged. This is the only
era lookup in the library, and the other symbol tables (months, weekdays,
am/pm) are shared by all three calendars. The `yyyy` padding of the Imperial
year still differs from `SimpleDateFormat` (`0006` against `6`); that is the
year rule and is left alone here.
Repro:
```java
FastDateFormat.getInstance("G yyyy", TimeZones.GMT, new Locale("ja", "JP",
"JP")).format(date20240501);
```
Expected: `令和 0006`, and `parse` accepts it again.
Actual: `ArrayIndexOutOfBoundsException: Index 5 out of bounds for length
2`; the `th_TH` form prints `ค.ศ. 2567` and no longer parses.
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