Because you can extend at most one other class (recall from Part 1 that Java doesn’t support class-based multiple inheritance), you’re not forced to explicitly extend Object; otherwise, you ...

Java supports single inheritance through class extension, in which one class directly inherits accessible fields and methods from another class by extending that class.

Java does enable the option to mark a class as final to eliminate the ability to perform inheritance complete, but that is often too heavy of a hammer to drop. Marking a class as final prevents all ...