When looking into something else, Ana [~amihalceanu] ran into a test failure in test/jdk/java/text/Format/NumberFormat/Bug4944439.java. Several test methods in that test fail on her local system with exceptions like:

18:47:58.418] STARTED Bug4944439::parseLongTest '[1] -9223372036854775808.00'
org.opentest4j.AssertionFailedError: DecimalFormat.parse("%s") did not return Long ==> Unexpected type, expected: <java.lang.Long> but was: <java.lang.Double>
    at org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:151)
    at org.junit.jupiter.api.AssertionFailureBuilder.buildAndThrow(AssertionFailureBuilder.java:132)
    at org.junit.jupiter.api.AssertInstanceOf.assertInstanceOf(AssertInstanceOf.java:49)
    at org.junit.jupiter.api.AssertInstanceOf.assertInstanceOf(AssertInstanceOf.java:35)
    at org.junit.jupiter.api.Assertions.assertInstanceOf(Assertions.java:3630)
    at Bug4944439.parseLongTest(Bug4944439.java:73)

A bit of investigation reveals that the default locale on her system is "en_NL" which causes these failures.

Interestingly, the test seems to configure the default locale to Locale.US to avoid these issues, in its BeforeAll method:

    // Save JVM default locale
    private static final Locale savedLocale = Locale.getDefault();
    private static final DecimalFormat df = new DecimalFormat();

    // Set JVM default locale to US for testing
    @BeforeAll
    static void initAll() {
        Locale.setDefault(Locale.US);
    }

    // Restore JVM default locale
    @AfterAll
    static void tearDownAll() {
        Locale.setDefault(savedLocale);
    }

However, notice that the DecimalFormat instance is already constructed as a final field before the default Locale is switched to Locale.US. So the DecimalFormat instance used in the test ends up using a non-US locale causing this failure.

This looks like an oversight in the test when some of these tests were converted to JUnit through JDK-8317372 (it would be good to check if other tests in that changeset might have similar issue).