composite inheritance: how to assign a final field at sub-class constructor which depends on 'this' value (backward reference)?

Question

I use composite classes to group functionalities.
But, the class A (with composite A1), got inherited by B (with composite B1), and a behavior existent at A1 is going to be

Answer 1

With this tip, given by @KevinHooke, I found this answer and I came with this code below.

But be aware that this option I chose may cause trouble.

So I ended up using an overriden method to instantiate the "1" kind, letting the super class take care of the assignment.

class finalFieldTestWorks{
    class A1{A1(A a){}}

    class A{
      protected final A1 a1;
      A(){
        this.a1=new1();
      }
      protected A1 new1(){return new A1(this);}
    }

    class B1 extends A1{B1(B b){super(b);}}

    class B extends A{
      B(){
        super();
      }
      @Override
      protected B1 new1(){return new B1(this);}
    }
}

PS.: Other tips/workarounds will be appreciated.