Classes, the templates used to create objects that can store data and accomplish tasks, turn up in everything you do with the Java language.
Today, you extend your knowledge of classes by learning more about how to create them, use them, organize them, and establish rules for how other classes can use them.
The following subjects are covered:
Controlling access to methods and variables from outside a class
Finalizing classes, methods, and variables so that their values or definitions cannot be subclasses or cannot be overridden
Creating abstract classes and methods for factoring common behavior into superclasses
Grouping classes into packages
Using interfaces to bridge gaps in a class hierarchy ...