Chapter 5
Inheritance: Is That All I Get?
IN THIS CHAPTER
Including constructors in a hierarchy
Invoking the base-class constructor
Differentiating between is a and has a
Substituting one class object for another
Object-oriented programming is based on four principles: the capability to control access (encapsulation), inherit from other classes, respond appropriately (polymorphism), and refer from one object to another indirectly (interfaces).
Inheritance is a common concept. You are a human. You inherit certain properties from the class Human, such as your ability to converse and your dependence on air, food, and beverages. The class Human inherits its dependencies on air, water, and nourishment from the class Mammal, which inherits from the class Animal.
The capability to pass down properties is a powerful one. You can use it to describe items in an economical way. For example, if your son asks, “What's a duck?” you can say, “It’s a bird that quacks.” Despite what you may think, that answer conveys a considerable amount of information. Your son knows what a bird is, and now he ...