how much should i know about java to start learning android studio

Answer 1

practically only the basics are enough, however you will only be able to do very simple stuff

Answer 2

A modified Java is used in Android Studio. So, basics are enough.

Answer 3

the basics are enough

but with basics i mean basically the whole syntax of the language, you should be familiar with classes, inheritance, polymorphism, abstract classes, interfaces, etc
knowing about some advanced topics like file access and threads can be useful, but you can as well just learn it when you need it with android
but if you know that it should not be a problem, google has great resources for learning
if you know java you basically just have to research what classes the android api contains and how to use then