Question

Sorry for the bad title, but I couldn’t think of a better one.

I’m having a class A and a class B which is kind of a sub class of A, like so:

(Is there actually a correct name for it? Isn’t ‘sub class’ reserved for inheritance?)

class A {     int i = 0;     class B {         int j = 1;     } }  class Test {     public static void main() {         A a = new A();         B b = a.new B();         A c = ??? b ??? // get 'a' back     } } 

From B every property of A can be accessed, therefore both, a.i and b.i, return 0. Now, I’m wondering whether it’s somehow possible to retrieve the original object of type A out of b, as b contains everything that a contains? Simple casting apparently doesn’t do the trick.

Second one:

class A {      void print() {         System.out.println('This is class A.');     }      class B {         void print() {             // <--- How to access print() of class A (like this.A.print() or smth)?              System.out.println('This is class B.');         }     } } 

You could alternatively also provide me with some good resources on this topic, as I’ve been too stupid to find a good one so far.

Thanks in advance. 🙂

Answer 1

There doesn’t seem to be a way to access the outer class from outside. But you can do it like this:

class A {     int i = 0;     class B {         final A outer = A.this;         int j = 1;     } }  class Test {     public static void main() {         A a = new A();         A.B b = a.new B();         A c = b.outer // get 'a' back     } } 

ClassName.this will be the instance of the outerclass associated with the instance of an inner class.