Many people have Java on their computers and will receive the reminders to update it on a regular basis which you should do.
However many people do not need it and will never miss it if you uninstall it.
Java has been used by some financial institutions including the ATO so if you submit your BAS online from your computer you will be stuck with it.
It is also used with some online games.
For everyone else go to programs in your control panel and uninstall it as outdated Java installs can lead to your computer becoming infected.