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Principles of Computer Programming (using Java) Chapter 10 Subclasses. Haidong Xue Summer 2011, at GSU. Content. Inheritance Overriding Polymorphism The “Object” class. Inheritance. What is inheritance? What are the advantages of inheritance in Java? - PowerPoint PPT Presentation
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Principles of Computer Programming(using Java)
Chapter 10 Subclasses
Haidong XueSummer 2011, at GSU
Content• Inheritance• Overriding• Polymorphism• The “Object” class
Inheritance
• What is inheritance?• What are the advantages of inheritance in
Java?• How to make a class in Java using inheritance?• E.g.:
– TestInheritance.java, Vehicle.java, Car.java, Bike.java
Inheritance
Car
Data: speed, weight, gas amount, size of tires
Actions: show speed, show weight, accelerate, brake, add gas, show tire size
Inheritance
Bike
Data: speed, weight, size of tires, size of pedals
Actions: show speed, show weight, accelerate, brake, show tire size, show pedal size
Inheritance
Car
Data: speed, weight, gas amount, size of tires
Actions: show speed, show weight, accelerate, brake, add gas, show tire size
Bike
Data: speed, weight, size of tires, size of pedals
Actions: show speed, show weight, accelerate, brake, show tire size, show pedal size
Inheritance
Car Bike
Vehicle
Data: speed, weight, size of tires
Actions: show speed, show weight, accelerate, brake, show tire size
Data: gas amount
Actions: add gas
Data: size of pedals
Actions: show pedal size
extends
• TestInheritance.java• Vehicle.java• Car.java• Bike.java
Inheritance
Overriding
• If a method in the subclass has the same signature of a method in the superclass, the method in the superclass is hided and overridden.
• E.g.:– TestOverriding.java– Vehicle.java, Car.java, Bike.java
Polymorphism
• An ability of a programming language;• an instance of a subclass can take the place
of an instance of any of its superclasses;• if an object variable of the superclass points to
a subclass object, when calling an overridden method, the method of the subclass will be called.
The punch game
• InstructorsInCSC2310.java
The Object class
• What is Object class?• A rule: all the classes have to have a superclass.• The Object class is the default superclass.• What are the advantages?
– One type for all;– Some common method for all the objects, like toString().
The bonus assignment
• Worth: 10 points in the final grade• Develop a program to play Texas Holdem
Poker
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