It was ok in the past but something has broken some months ago and my bank client authentication Java applet stopped working. Now I have to reboot to Windows and use it from there. I have installed (and am using for different purposes) Oracle JDK (manually, from official Oracle distribution files) on XUbuntu but I think Firefox Java plugin still uses OpenJDK. How to set up and make sure Firefox to use a specific Oracle JDK?
Thanks to @fossfreedom, I've set up Firefox to use Oracle JDK as follows:
Unfortunately this haven't solved my actual problem - banking still doesn't work (fails to log-in with correct key file and password).