RFR: JDK-8316435: sun.util.calendar.CalendarSystem subclassing should be restricted [v5]

[Naoto Sato]

On Wed, 20 Sep 2023 08:54:55 GMT, Andrey Turbanov <aturbanov at openjdk.org> wrote:

>> Justin Lu has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - cleanup CalendarDate after revert
>>  - Revert "Replace sprintf0d with Formatter"
>>    
>>    This reverts commit 84a346aed2be262b717f82fbbc32a4ed0323bccc.
>
> src/java.base/share/classes/sun/util/calendar/CalendarDate.java line 63:
> 
>> 61:  */
>> 62: public sealed abstract class CalendarDate implements Cloneable
>> 63:         permits BaseCalendar.Date {
> 
> Can we just merge `CalendarDate` and `BaseCalendar.Date` to be the one class?
> I think it will greatly simplify the code.

`BaseCalendar` is for Gregorian based calendars, so its `Date` class also represents dates for those calendars, while `CalendarDate` is an abstract class for all calendar implementations. So I don't think merging them is the right direction.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15803#discussion_r1331943059