This week's book giveaway is in the Java in General forum. We're giving away four copies of Beginning Java 17 Fundamentals: Object-Oriented Programming in Java 17 and have ishori Sharan & Adam L Davis on-line! See this thread for details.
You are correct that this is part of a learning experience.There is no need for address to point back to customer.Let's say there are 2 entities A & B which have a bi-directional association. In that case I think shared primary key will be the preferred technique.