In JDK 9 then the extension and application class loaders will not be URLClassLoaders. This test makes the assumption that the system/application class loader is a URLClassLoader and so fails with a CCE. The test needs to be re-examined.

java.lang.ClassCastException: sun.misc.Launcher$AppClassLoader cannot be cast to java.net.URLClassLoader
at SubclassGC.main(SubclassGC.java:53)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.sun.javatest.regtest.MainWrapper$MainThread.run(MainWrapper.java:94)
at java.lang.Thread.run(Thread.java:745)