Learn the differences between these Java language elements and how ... Can have any kind of instance or static variables, mutable or immutable. A class can implement multiple interfaces.

but every instance of a bank account has a different number. The account ID is constant on a per-account basis, but it's not the same for every account. That's how final variables work. What is a ...

Therefore, learning about variables in Java should be ... interact with their class (instance variables vs static variables). You won’t need to understand these differences for a while, but ...