They are all used in the real world. You don’t have to learn the details of any of them.
You need to know how to find methods, constructors, etc, in the API documentation, and you need to find a tutorial about them. Like
this one, for example.
Since many of those methods and constructors declare checked exceptions, you need to know about exceptions, the <> syntax, try-with-resources, etc., too.
It is worth learning when you can get problems with a
null reference to a Console.