Cassandra fails to start without the following jvm options from jvm-11-server.options:

-Djdk.attach.allowAttachSelf= true --add-exports java.base/jdk.internal.misc=ALL-UNNAMED --add-exports java.base/jdk.internal.ref=ALL-UNNAMED --add-exports java.base/sun.nio.ch=ALL-UNNAMED --add-exports java.management.rmi/com.sun.jmx.remote.internal.rmi=ALL-UNNAMED --add-exports java.rmi/sun.rmi.registry=ALL-UNNAMED --add-exports java.rmi/sun.rmi.server=ALL-UNNAMED --add-exports java.sql/java.sql=ALL-UNNAMED --add-opens java.base/java.lang.module=ALL-UNNAMED --add-opens java.base/jdk.internal.loader=ALL-UNNAMED --add-opens java.base/jdk.internal.ref=ALL-UNNAMED --add-opens java.base/jdk.internal.reflect=ALL-UNNAMED --add-opens java.base/jdk.internal.math=ALL-UNNAMED --add-opens java.base/jdk.internal.module=ALL-UNNAMED --add-opens java.base/jdk.internal.util.jar=ALL-UNNAMED --add-opens jdk.management/com.sun.management.internal=ALL-UNNAMED

Without these options the following stack trace appears and prevents startup

2020-01-05T17:42:15,009 ERROR main org.apache.cassandra.service.CassandraDaemon Exception encountered during startup java.lang.ExceptionInInitializerError at org.apache.cassandra.config.DatabaseDescriptor.guessFileStore(DatabaseDescriptor.java:1127) at org.apache.cassandra.config.DatabaseDescriptor.applySimpleConfig(DatabaseDescriptor.java:541) at org.apache.cassandra.config.DatabaseDescriptor.applyAll(DatabaseDescriptor.java:340) at org.apache.cassandra.config.DatabaseDescriptor.daemonInitialization(DatabaseDescriptor.java:168) at org.apache.cassandra.config.DatabaseDescriptor.daemonInitialization(DatabaseDescriptor.java:152) at org.apache.cassandra.service.CassandraDaemon.applyConfig(CassandraDaemon.java:665) at org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:609) at org.jesterj.ingest.persistence.Cassandra.start(Cassandra.java:135) at org.jesterj.ingest.scanners.SimpleFileScannerImplFTITest.testScanWithMemory(SimpleFileScannerImplFTITest.java:63) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28) at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:30) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222) at org.junit.runners.ParentRunner.run(ParentRunner.java:300) at org.junit.runner.JUnitCore.run(JUnitCore.java:157) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68) at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47) at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242) at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70) Caused by: java.lang.RuntimeException: java.lang.IllegalAccessException: access to public member failed: jdk.internal.ref.Cleaner.clean[Ljava.lang. Object ;@779dfe55/invokeVirtual, from org.apache.cassandra.io.util.FileUtils (unnamed module @2eda0940) at org.apache.cassandra.io.util.FileUtils.<clinit>(FileUtils.java:95) ... 33 more Caused by: java.lang.IllegalAccessException: access to public member failed: jdk.internal.ref.Cleaner.clean[Ljava.lang. Object ;@779dfe55/invokeVirtual, from org.apache.cassandra.io.util.FileUtils (unnamed module @2eda0940) at java.base/java.lang.invoke.MemberName.makeAccessException(MemberName.java:942) at java.base/java.lang.invoke.MethodHandles$Lookup.checkAccess(MethodHandles.java:2206) at java.base/java.lang.invoke.MethodHandles$Lookup.checkMethod(MethodHandles.java:2146) at java.base/java.lang.invoke.MethodHandles$Lookup.getDirectMethodCommon(MethodHandles.java:2290) at java.base/java.lang.invoke.MethodHandles$Lookup.getDirectMethodNoSecurityManager(MethodHandles.java:2283) at java.base/java.lang.invoke.MethodHandles$Lookup.unreflect(MethodHandles.java:1747) at org.apache.cassandra.io.util.FileUtils.<clinit>(FileUtils.java:86) ... 33 more

Use of --add-exports is described in the oracle documentation as

You may use the --add-exports option as a temporary workaround to compile source code with references to JDK internal classes.

which implies that this will not work forever. Also the code in FileUtils seems somewhat confused as it prints out a warning, as if it means to allow startup with a lower performance expectation, and then throws an exception that entirely prevents startup.