<i18n dev> RFR: JDK-8316435: sun.util.calendar.CalendarSystem subclassing should be restricted [v5]

[Andrey Turbanov]

On Wed, 20 Sep 2023 07:00:23 GMT, Justin Lu <jlu at openjdk.org> wrote:

>> Please review this PR which restricts sub-classing of the internal calendar system in sun.util.calendar to only the existing implementations. Drive by cleanup included.
>> 
>> As the implementation is long-standing and complete with no intent for future sub-classing, the CalendarSystem should be made sealed. Modifiers adjusted accordingly (`JulianCalendar.Date` must now have package visibility).
>> 
>> 
>> This system has the following structure,
>> 
>> `CalendarSystem` extended by `AbstractCalendar` extended by `BaseCalendar` extended by 
>> (`Gregorian, JulianCalendar, LocalGregorianCalendar`)
>> 
>> `CalendarDate` extended by `BaseCalendar.Date` extended by 
>> (`Gregorian.Date, ImmutableGregorianDate, JulianCalendar.Date, LocalGregorianCalendar.Date`)
>> 
>> Additionally, CalendarUtils was made `final`, as it is a utility class composed of static util methods.
>
> 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.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/15803#discussion_r1331283073