Class Design
Jeanne Boyarsky, Scott Selikoff · 2019
This chapter explains how class structure and inheritance is one of the most powerful features in the Java language. At its core, proper Java class design is about code reusability, increased functionality, and standardization. For example, by creating a new class that extends an existing class, you may gain access to a slew of inherited primitives, objects, and methods, which increases code reuse. Through polymorphism, you may also gain access to a dynamic hierarchy that supports replacing method implementations in subclasses at runtime. This chapter is the culmination of some of the most important topics in Java including class design, constructor overloading and inheritance, order of initialization, overriding/ hiding methods, and polymorphism. When creating a new class in Java, you can define the class as inheriting from an existing class. Inheritance is the process by which a subclass automatically includes any public or protected members of the class, including primitives, objects, or methods, defined in the parent class. For illustrative purposes, we refer to any class that inherits from another class as a subclass or child class, as it is considered a descendant of that class. Alternatively, we refer to the class that the child inherits from as the superclass or parent class, as it is considered an ancestor of the class.