PRESENTATION NAME

Java@Ch11. Inheritance and Polymorphism

2010.12.31

Outline

•Inheritance

•Superclasses and Subclasses

•Using super keyword

•Overiding Method

•Overiding vs. Overloading

•Dynamic Binding

•Polymorphism

[Sample code]

Novice.java、Magician.java 、Swordman.java 、Game.java

DynamicBindingDemo.java

Inheritance

• Object-oriented programming allows you to derivenew classes from existing classes. This is calledinheritance.

Superclasses and Subclasses

magic_attack()

power_attack()

Novice

Magician

Swordman

attack()

inheritance

程式範例:

 Novice.java、Magician.java 、

Swordman.java 、Game.java

Using super keyword

• The super refers to the superclass of the class in which superappears.

•It can be used in two ways:

1. To call a superclass constructor.

2. To call a superclass method.

Overiding Method

Novice

attack()

Archer

inheritance

overriding

程式範例:

Archer.java

Overiding vs. Overloading

•Overriding 覆寫

 Sometimes it is necessary for the subclass to modify the

implementation of a method defined in the superclass.

•Overloading 多載

Define multiple methods with the same name but different

signature .

(課本 p.407)

Dynamic Binding

•Dynamic Binding 動態載入

物件的行為並不是在編譯時期 (compiler-time)就已經決定了。而是在程式執行時期於(run-time)才動態地決定的。如何動態地決定。就看物件當時的狀態(state)而定，物件封裝了所有可能的狀態處理方法，並且根據外邊送來的訊息做出適當的反應。

(課本 p.409)

程式範例:

 DynamicBindingDemo.java

程式範例:

 DynamicBindingDemo.java

Polymorphism

• Polymorphism 多型

 簡單來說，多型是指一個物件可以擁有多個不同的型態，而這些型態必須是該物件所繼承的其他類別。

Organism O = new Organism();

People P = new People();

Organism O2 = new People();

生物

動物

人

extends

• Polymorphism

- Overriding

- Overloading

- Dynamic binding

- Interface/abstract

ArrayList

•ArrayList class that can be used to store an unlimited numberof objects.

add(o object): void

add(index: int, o: object): void

clear(): void

indexOf(o: object): int

isEmpty(): boolean

lastIndexOf(o: object): int

remove(o: obect): boolean

size(): int

Java.util.ArrayList

程式範例:

TestArrayList.java