Hi Bernd,

As you pointed out, the change you see here is the result of this change in JDK9:

https://bugs.openjdk.java.net/browse/JDK-8008577

where the default locale provider was switched to CLDR. Although we don't describe those behavior changes in the spec (as it is regarded as l10n changes which may differ across implementations), it was generally noted in JDK9's release note:

---
As a result, users may see differences in locale sensitive services behavior and/or translations. [1]
---

You can use the COMPAT provider through the java.locale.providers system property if you need the pre-JDK9 behavior.

HTH,
Naoto

[1] https://www.oracle.com/java/technologies/javase/v9-issues-relnotes.html

On 7/31/20 1:17 PM, Bernd Eckenfels wrote:
Hello,

Just wanted to mention a thing I noticed when switching from 8 to 11. I knew 
before that the Locale data provider has changed, and I could notice that for 
example in the writing style for abbreviated words in dates. However something 
I did not expect is, that the definition of Calemdars change as well.

Locale.GERMAN and Locale.GERMANY construct different calemdars under Java 11 
with CLDR as opposed to Java 8 or Java 11 with compat. The most notably changes 
are when calculating calendar weeks (min days in first week) or the start of a 
week (Sunday vs. Monday).

I haven't seen that explicitely mentioned and I also wonder if this should be 
mentioned in the Locale JavaDoc that language locales and country locales might 
differ severely in that aspect.


GERMANY:
Calendar.minDays 4 
java.util.GregorianCalendar[time=1596218932830,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=…,firstDayOfWeek=2,minimalDaysInFirstWeek=4,ERA=1,YEAR=2020,MONTH=6,WEEK_OF_YEAR=31,WEEK_OF_MONTH=5,DAY_OF_MONTH=31,DAY_OF_YEAR=213,DAY_OF_WEEK=6,DAY_OF_WEEK_IN_MONTH=5,AM_PM=1,HOUR=8,HOUR_OF_DAY=20,MINUTE=8,SECOND=52,MILLISECOND=830,ZONE_OFFSET=3600000,DST_OFFSET=3600000]
11.0.1+13-LTS de_DE 2011-01-01 2010-52

GERMAN
Calendar.minDays 1 
java.util.GregorianCalendar[time=1596218932879,areFieldsSet=true,areAllFieldsSet=true,lenient=true,zone=...,firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2020,MONTH=6,WEEK_OF_YEAR=31,WEEK_OF_MONTH=5,DAY_OF_MONTH=31,DAY_OF_YEAR=213,DAY_OF_WEEK=6,DAY_OF_WEEK_IN_MONTH=5,AM_PM=1,HOUR=8,HOUR_OF_DAY=20,MINUTE=8,SECOND=52,MILLISECOND=879,ZONE_OFFSET=3600000,DST_OFFSET=3600000]
11.0.1+13-LTS de    2011-01-01 2011-01

Sample code:

     Date d = new Date(1293843600000L);

     Locale l = Locale.GERMANY;

     Calendar c = Calendar.getInstance(l);
     System.out.println("Calendar.minDays "+ c.getMinimalDaysInFirstWeek() + " 
" + c);

     SimpleDateFormat sdf = newSimpleDateFormat("yyyy-MM-DD YYYY-ww", l);
     System.out.printf("%s %-5s %s%n", System.getProperty("java.vm.version"), 
l, sdf.format(d));


--
http://bernd.eckenfels.net

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