Safely call setter after getter chain eg foo.getX().getY().setZ(...);

How do I safely call setter after getter chain eg foo.getX().getY().setZ(...);? For example, suppose I have a nested POJO, and I want to be able to set a field of a nested object.

Foo foo = ...
foo.getX().getY().setZ(...);

I want the behavior to be such that if X and Y do not exist then they are created automatically; otherwise it reuses the existing object.

In other words, I want it to be behave equivalent to

Foo foo = ...
X x = foo.getX();
if (x == null) { 
  x = new X();
  foo.setX(x);
}

Y y = x.getY();
if (y == null) {
  y = newY();
  x.setY(y);
}

y.setZ(...);

I'm wondering if there is a trick out there using reflection/functional that comes close to this.

I also have the following constraints:

• I cannot modify any of the classes
• The solution must know about only the public getters and setters, not the private instance variables
• I want the getter to modify the internal state only when specifically requested; I don't want x = foo.getX() to modify foo.