Outerclass with its innerclass as an argument for the outerclass constructor

Question

Im wondering if it is possible to create this object based on the code below or is it a cyclic dependency which cant be solved?

public class A {
  private B b;

  public A(B b) {
    this.b = b;
  }

  public class B {
    public B() {}
  }
  
}

I was provided with a class which looked like this and I cant find a way to initialize B or A. Its like and impossible cycle.

Answer 1

If all you do with instance of B in A's constructor is an assignment, then you could try using null at instantiation and then hand it a B instance:

A a = new A(null);
A.B b = a.new B();
a.b = b;

the above requires a.b to be public, or you need to add a setter. But that looks bad to me, so perhaps you should make B class static, and by doing so it can be instantiated independently of A::

public class A {
    private B b;

    public A(B b) {
        this.b = b;
    }

    public static class B {
        public B() {}
    }
}

and then

A.B b = new A.B();
A a = new A(b);