Why do I need to use keyword "this" to call my enclosing methods or variables

Question

I have a doubt if I have a non-static nested class why do I need to use the keyword "this" to call a method or variable of my enclosing class? What I think is the following: if a non-static nested class can access to methods and variables of its enclosing class and a non-static nested object instance is already associated to its enclosing object instance why do I need to use "this"? For example I have the following code:

public class ClassA {

    public class ClassB {

        public void bye() {
            ClassA.this.hello();
            // Why not just ClassA.hello()?
        }
    }

    public void hello() {

    }
}

and if from a method of my enclosing class I want to call a method of one of mine non-static classes how should I do?For example if from my method hello() I want to call bye() how should I type?

Answer 1

First of all, you can simply call hello().

ClassA.hello() would look for a static method named hello() in ClassA. ClassA.this.hello() looks for an instance method.