Java DICOM viewer fails on MacOS Catalania (10.15.3) I have a CD containing the images of the MRT I had recently. I tried to start the DICOM viewer which is on the CD as well. However the viewer fails with the error: 

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.eclipse.osgi.internal.baseadaptor.BaseStorage (file:/Users/manuel/2016-11-18 - CT Josephskrankenhaus/PLUGINS/OSGI.JAR) to method java.net.URLClassLoader.addURL(java.net.URL)
WARNING: Please consider reporting this to the maintainers of org.eclipse.osgi.internal.baseadaptor.BaseStorage
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release


Return value is 13. How can I troubleshoot this problem?
These warnings are caused by Oracle tightening security in the JVM (which is unfortunately badly needed) but currently does not cause the process to crash.   

Hence my guess is that something else has broken.  Without anything further to go on, I would guess (based on the exit code 13) that the Java DICOM viewer is 1) rather old and 2) links in native code, notably Java 6 (perhaps even 5) and native 32-bit library.

Unfortunately for you, modern Java versions are 64-bit only, and cannot use 32-bit libraries, so if I'm right the Java you have now will not run this program.  You might, however, have luck in getting the old Java 6 from Apple and use that instead, but only if you have not upgraded to Catalina.

I would look around for a newer version of the DICOM viewer on the net.  You might be lucky.