Hi,
In a word - yes.
You will find that some websites require it too.
It is a form of programming language - if Hotmail, for instance, has used it then, if you haven't got it, Hotmail will not be able to function properly on your machine.
Java is not Javascript.
One of the security guys will give you better info re Java ...basically if you have it on your system you should keep it up to date for security reasons.
I hope this helps a little ?