Here is an illustration of the distribution of attributes and behaviors for the Book hierarchy. Each derived class should containĪttributes and behaviors specific to them. Organizing Attributes (Instance Variables) and Behaviors (Methods)Īttributes and behaviors that are common for all classes in the hierarchy should be placed in the parent class. This hierarchy of classes is implemented in the following examples. It is helpful to create a structure, as the one below, to aid in thinking about the hierarchy. TextBook is the parent of two derived classes, Novel, Comic, Dictionary, and TextBook are derived from Book. Remember that derived classes are more specific classes and that they can in turn have classes derived from them. The parent class will contain attributes and behaviors that areĬommon for all derived classes. When designing a class hierarchy, first determine the parent class and all of the derived classes. All Java objects are considered to be polymorphic as they share more than one IS-A relationship (at least all objects will pass the IS-A test for their own type and for the class Object). Polymorphism in OOP occurs when a super class references a sub class object. You can step through this code using the Java Visulaizer by clicking on the following link: Base Example.Thinking About the Book Hierarchy (Inheritance) Polymorphism is the ability of an object to take on many forms.
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