Like we said, Java source is really just classes. Import statements are shorthand for many different classes; and comments aren’t really there (as far as the compiler is concerned) in the first place. However there is one thing in Java source code that is neither a class nor a member of a class. That’s an interface. We’re not going to say much about interfaces yet since that’s a subject for a more advanced chapter. However we will note that an interface defines methods that a class implements. In other words it declares what certain classes do. However an interface itself does nothing. All the action at least, happens inside classes.