Inheritance, Superclasses, Subclasses

Inheritance Allows for more usability of code Page 168 of Heads First book Class – SuperHero (Classes) Suits; tights; specialPower (Methods) useSpecialPower; putOnSuit Think of Parent/Child Relationship The sub-class Inherits from the SuperClass In Java, we say the subclass extends the SuperClass.

Overriding Methods You have the ability to override the method that are received from the parent. What you override is then specific to that subclass. SuperClass – class that is inherited from – more abstract Subclass – the specific “children” of the superclass.

Page 169 Example - Public class FamilyDoctor extends Doctor { Doctor – superclass Subclasses – Family Doctor, Surgeon Any subclass of Doctor will have a WorksAtHospital & a treatPatient property Extends – means “inherits from” CODE Public class FamilyDoctor extends Doctor { Can then put items specific to that class

Surgeon – page 169 Look at surgeon class TreatPatient method overrides the TreatPatient method in doctor class. A surgeon treats a patient by performing surgery, so that method overrides the method in Doctor class. Surgeon also has a MakeIncision method

Page 170 – Inheritance Tree Design Look for objects that have common attributes and behaviors Use inheritance to avoid duplicating code in subclasses. Design a class that represents the common state and behavior All Animals – have a picture; eat food, have hunger, etc.

Inheritance Tree, cont’d Decide if a subclass needs behaviors (method implementations) that are specific to that particular subclass type. MakeNoise and Eat are specific to each type of animal. Look for more opportunities to use abstraction, by finding two or more subclasses that might need common behavior.

Page 174 Finish the class Hierarchy Since animals already have an organizational hierarchy, that makes the most sense for class design. Felines – lion, tiger, cat (can use a common roam method) Canine – wolf, dog (can use a common roam method)