RFR: 8367901: Calendar.roll(hour, 24) returns wrong result [v2]

[Justin Lu]

On Thu, 18 Sep 2025 15:39:25 GMT, Naoto Sato <naoto at openjdk.org> wrote:

>> Justin Lu has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  -  + - to - in comment
>>  - DST test cases + compute expected value as method + improve err msg
>
> test/jdk/java/util/Calendar/RollHoursTest.java line 56:
> 
>> 54:     @FieldSource("hours")
>> 55:     void HourOfDayTest(int hour) {
>> 56:         var cal = new GregorianCalendar(2005, 8, 12, PM_HOUR, 30, 45);
> 
> IIUC, the regression was caused by the fix to [JDK-8152077](https://bugs.openjdk.org/browse/JDK-8152077), where it jiggles an hour on the transition day. So although I don't think it would fail, but it might be helpful to test on one of those days

Good point. Added both _standard -> daylight savings_ and _daylight savings -> standard_ test cases to be thorough, although the former one is the interesting test case.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27355#discussion_r2361133554