Maintaining a two way relationship between classes

Question

It is pretty common, especially in applications with an ORM, to have a two way mapping between classes. Like this:

public class Product
{
    private List

        

Answer 1

In the past I've added "link" methods, i.e., instead of "setting" the Price on a Product, you link the product and the price.

public void linkPrice(Price toLink) {
    this.price = toLink;
    toLink.setProduct(this);
}

(if you use setPrice to do this, then setProduct would also do this, and they would forever call each other in the second line, hence I create an explicit link method instead of using the setters and getters. Indeed the setter could be package protected.

YMMV, your situation could be different.