Please review this PR which restricts sub-classing of the internal calendar system in sun.util.calendar to only the existing implementations.
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. ------------- Commit messages: - private constructor in CalendarUtils - Make utility class 'CalendarUtils' final - Copyright years - Seal the rest of the 'CalendarSystem' - Clarify public for LCG.date, when other BaseCalendar.date inheritors are default - Seal BaseCalendar and make inheritors final - Seal BaseCalendar.Date and make inheritors final Changes: https://git.openjdk.org/jdk/pull/15803/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15803&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8316435 Stats: 40 lines in 9 files changed: 7 ins; 0 del; 33 mod Patch: https://git.openjdk.org/jdk/pull/15803.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/15803/head:pull/15803 PR: https://git.openjdk.org/jdk/pull/15803
