A DESCRIPTION OF THE PROBLEM :
Hi.
In your latest jdk15 versions, we found something not quite right.
a related pr is at https://github.com/apache/commons-lang/pull/558
In short, some codes like this cannot pass tests for some Locale like  "ff_LR_#Adlm"
 
BUT in jdk 8-14's all locales can pass the tests, only ones newlly added in jdk15 fails.
I wanna know whether it be by design or just a bug.

REGRESSION : Last worked in version 14.0.1

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the tests below with Junit.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
tests pass
ACTUAL -
tests failed

---------- BEGIN SOURCE ----------
    @Test
    public void java15BuggyLocaleTestAll() throws ParseException {
        for (final Locale locale : Locale.getAvailableLocales()) {
            testSingleLocale(locale);
        }
    }

    @Test
    public void java15BuggyLocaleTest() throws ParseException {
        final String buggyLocaleName = "ff_LR_#Adlm";
        Locale buggyLocale = null;
        for (final Locale locale : Locale.getAvailableLocales()) {
            if (buggyLocaleName.equals(locale.toString())) {
                buggyLocale = locale;
                break;
            }
        }
        if (buggyLocale == null) {
            return;
        }
        testSingleLocale(buggyLocale);
    }

    private void testSingleLocale(Locale locale) throws ParseException {
        final Calendar cal = Calendar.getInstance(GMT);
        cal.clear();
        cal.set(2003, Calendar.FEBRUARY, 10);
        final SimpleDateFormat sdf = new SimpleDateFormat(LONG_FORMAT, locale);
        final String formattedDate = sdf.format(cal.getTime());
        sdf.parse(formattedDate);
        sdf.parse(formattedDate.toUpperCase(locale));
        sdf.parse(formattedDate.toLowerCase(locale));
    }
---------- END SOURCE ----------

FREQUENCY : always