It is not the first time in this book that we present an example of Sealed Classes and switch expressions. In Chapter 2, Problem 61, we have briefly introduced such an example via the sealed Player interface with the goal of covering completeness (type coverage) in pattern labels for switch.If, at that time, you found this example confusing I’m pretty sure that now is clear. However, let’s keep things fresh and let’s have another example starting from this abstract base class