I'm not sure whether I can post this question here or not. I have an application deployed into my tomcat server and the application is running fine. Now if I have to upgrade my java version, does it stop my application? In other words Do I need any downtime for upgrading my java version?
Now if I have to upgrade my java version, does it stop my application until my upgrade completed?
That would be advisable.
You probably could install a newer version of Java with the existing one is being used to run your application. However, you will need to restart Tomcat and your application for them to start using the newly installed JRE.
Do I need any downtime for upgrading my java version?
You certainly need some down time.
However, as @Andreas says in a comment, if you design your system(s) appropriately, you may be able to implement a system with a live server and a "hot" stand-by server, and use a load-balancer or haproxy to "fail over" from one system to the other quickly enough that the interruption is too short to notice. Alternatively, if you have multiple "live" instances of the server you can take instances out of service, upgrade them and then reintroduce them.