i don't understand the parameter of the method isLargerThan.
what does it mean to pass a "Relatable" object into the method?
what is an object of an interface??
in fact, it's kind of the point of interfaces. You can use ANY class that implements that type. This may not seem like it has much use right now...but say in a year someone comes up with some brand new class (this happens all the time when you license software from third parties) that has better performance than what you are currently using. You can drop that new code in and not touch this code at all, as long as the new class implements your interface.
There are only two hard things in computer science: cache invalidation, naming things, and off-by-one errors