page 96 & 104, "argument" should be "parameter"
Now imagine a test class has a method with a declared argument type of GameShape, which means it can take any kind of GameShape.
The key point is that the doShapes() method is declared with a GameShape argument but can be passed any subtype (in this example, a subclass) of GameShape.
Of course, the cool thing here is that any class from any inheritance tree can also implement Animatable, so that means if you have a method with an argument declared as type Animatable, you can pass in PlayerPiece objects, SpinningLogo objects, and anything else that’s an instance of a class that implements Animatable
reference page 49 of OCA Java SE 8 Programmer I Exam Guide (Exams 1Z0-808)
As a bit of background, we’d like to clarify how we’re going to use the terms “argument” and “parameter” throughout this book:
arguments The things you specify between the parentheses when you’re invoking a method:
parameters The things in the method’s signature that indicate what the method must receive when it’s invoked: