Why can't I access methods through a class?

Question

OOP

there is a class A which has private field getters, for example public int getX() {retutn this.x} . When I access the getX() method from class B through class A, that is, A.getX(), then an error occurs, and when I declare a class variable of type A a, the compiler already sees the method through a.getX().
1. Please explain what is the joke here.
2. Declaration of variables like object can be stored on the heap before initialization?

Answer 1

Only static methods can be called through the class name.

Answer 2

Who knows. It can be assumed that you are accessing a method without creating an object. And how does he know in this case - what is this.x?