The purpose of the book is to prepare you for the exam. This question is about using a List implementation. The question makes it clear, that the real implementation of a HenHouse object doesn't matter. What matters are four possible return values of the method getChickens: empty list, null, a list with one element and a list with multiple elements. If you use System.exit, you will not have any return value at all. Even Oracle doesn't make such traps, thanks god! So don't think to much. Everything is gonna be ok!