That's not Java. Java has never been used on that page.
What seems to happen with IMC is that when you go to a Device Details page, it goes and does some extra polling of that device, and it will try and login to it. If you have incorrect SNMP credentials, it will take a while to time out. If the devices are on the far end of a high-latency link, then it can take a while, and you'll see it sitting there spinning for a bit. Once it's got whatever info it is after, it loads the rest of that page
But if the device has all the right SNMP + Telnet/SSH credentials, and latency is low, it should not take long at all for that page to load. Double-check all credentials. Click Synchronise, the Refresh, and ensure the System Uptime value is updated. Run a backup, and check credentials are working.
You don't _have_ to use a JRE any more, with the introduction of HTML5. But it's still there on some pages, such as Resource -> Network Topology. Don't know why, since if you view the Topology via Resource -> Custom View, it uses HTML5.
If you do have a JRE installed on your client systems, you should use the latest available, and patch it frequently, as there are so many security issues with it. You shouldn't touch the JRE used by IMC on the server side.