testcase testFlatMappingClose was newly introduced in JDK-8071600 in CollectorsTest, it failed in SAND testing.
Test should be marked as serialization-hostile

java.lang.AssertionError: expected [0] but found [2]
at org.testng.Assert.fail(Assert.java:89)
at org.testng.Assert.failNotEquals(Assert.java:489)
at org.testng.Assert.assertEquals(Assert.java:118)
at org.testng.Assert.assertEquals(Assert.java:365)
at org.testng.Assert.assertEquals(Assert.java:375)
at org.openjdk.tests.java.util.stream.CollectorsTest.testFlatMappingClose(CollectorsTest.java:526)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:502)
at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:80)
at org.testng.internal.Invoker.invokeMethod(Invoker.java:715)
at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:907)
at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1237)
at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:127)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:111)
at org.testng.TestRunner.privateRun(TestRunner.java:767)
at org.testng.TestRunner.run(TestRunner.java:617)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:334)
at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:329)
at org.testng.SuiteRunner.privateRun(SuiteRunner.java:291)
at org.testng.SuiteRunner.run(SuiteRunner.java:240)
at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:51)
at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:85)
at org.testng.TestNG.runSuitesSequentially(TestNG.java:1197)
at org.testng.TestNG.runSuitesLocally(TestNG.java:1122)
at org.testng.TestNG.run(TestNG.java:1030)
at org.testng.TestNG.privateMain(TestNG.java:1337)
at org.testng.TestNG.main(TestNG.java:1306)