Inheritance and Polymorphism

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 derive new classes from existing classes. This is called inheritance.

Superclasses and Subclasses HP MP magic_attack()power_attack() Novice MagicianSwordman 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 super appears. It can be used in two ways: 1. To call a superclass constructor. 2. To call a superclass method.

Overiding Method HP MP 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 number of 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