I think perhaps I was a little too aggressive in framing this issue. I should have scaled it back a little bit to focus on the UI issue, not the java classes. The title may need changing, and it may require filing another issue. I see two problems. With OpenJDK, the file descriptor info and the JVM memory info are not showing on the dashboard. Side note: I don't have OpenJDK running anywhere and don't have unallocated hardware I can fiddle with right now.
The underlying issue is that the user says the file descriptor info is not found in /admin/system output running under OpenJDK, but it is there under Apple or Oracle JVMs. If the info is available at all from OpenJDK, it may require a code change to get it.