Are they really necessary?

discuss ......

Java is a huge security problem so best bet is to turn it off if you can. Apple Mac's don't have Java installed by default any more for this reason (been this way for a few years now).

If you do need Java (not to be confused with Javascript which is completely different despite the name) then you can install it. If installed then it is important to keep it up to date so that you get the benefit of the latest security patches.

Very few people need to have Java installed these days so turn it off and see if any of your applications stop working is my advice.

Cheers,
Craig.