Java - How to handle very similar classes with nested classes

Hi All,

 I am having difficulties to handle the following classes gracefully:

Suppose I have the following class A:

class A{

	B b1;
	
	class B{
		
		C c1;
		D d1;
		
		class C{
		.
		.
		.
		}
		
		class D{
		.
		.
		.
		}
	
	}
}

Select allOpen in new window

and I have also class AA:

class AA{

	B b1;
	
	class B{
		
		C c1;
		E e1;
		
		class C{
		.
		.
		.
		}
		
		class E{
		.
		.
		.
		}
	
	}
}

Select allOpen in new window

I need to create and initialize objects of A or AA depending on some flag state.
Notice that class B inside class A is nesting class D whereas class B inside class AA is nesting class E !

The automatic thought I had is to derive them from some base class and use a factory.
Then I would get an object which I can use, but then I would face the need to work with D or E objects.
But I don't know exactly how to implement this idea. Is it possible at all? Is there a better way of achieving it?

Thank you!