Are there elements (methods, classes etc.) that are specific for Android Java that are not used in 'regular' Java - or vice versa?

Answer 1

Yes. Android has its own set of libraries alongside Java ones. Some Java libraries won't work on it and vise versa. You can learn Android alongside Java if you want, but it's usually preferred you do just Java first, so you have a better understanding when you tackle Android.

Answer 2

no not like that if we need in our Android app we can include that also