Hi, sorry for the lack of knowledge, maybe this is a stupid question. Is it necessary to install java after installing Ubuntu for the correct operation of the system? I mean for a standard user who only uses the pc for some tricks and basic things.
No it is not, and certainly not after a full install. I used Ubuntu for the past year without a need for Java until recently when I needed to install it for a Java programming course. Aside from that it never came up.
There are applications in the Software Centre that say they use Java, but I would assume if you install them the required Java libraries would be installed as dependancies.