類的高級特性

1、3、類的高級特性(抽象類、接口等)引入：本章繼續(xù)深入學(xué)習(xí)面向?qū)ο笏枷?。正課：1、抽象類并不是所有的類都是用來描繪對象的，如果一個類中沒有包含足夠的信息 來描繪一個具體的對象，這樣的類就是抽象類。用abstract修飾。定義抽象類：abstract class類名稱成員變量；方法();/定義一般方法abstract方法();定義抽象方法范例 testabstract :package testabstract;public abstract class Ani malpublic Ani mal(Stri ng aType)type = new Strin g(aType);public Str

2、i ng toStri ng()return "This is a " + type;/ Dummy method to be implemented in the derived classes public abstract void soun d();private String type; package testabstract;public class Cat exte nds Ani malpublic Cat(Stri ng aName)super("Cat"); / Call the base con structor n ame =

3、aName; / Supplied n ame breed = "Unknown" / Default breed valuepublic Cat(Stri ng aName, String aBreed)super("Cat"); / Call the base con structor n ame = aName;/ Supplied n amebreed = aBreed; / Supplied breed/ Return a String full of a cat's detailspublic Stri ng toStri ng()r

4、eturn super.toString() + "nit's " + name + " the " + breed;/ A miaowi ng methodpublic void soun d()System.out.pri ntln ("Miiaooww");private String name; / Name of a catprivate String breed; / Cat breed package testabstract;public class Dog exte nds Ani malpublic Dog

5、(Stri ng aName)super("Dog");con structorn ame = aName;/ Call thebase/ Supplied n amebreed = "Unknown"/ Default breed valuepublic Dog(String aName, String aBreed)/ Call thebasesuper("Dog");con structorn ame = aName;breed = aBreed;/ Supplied n ame/ Supplied breed/ Prese n

6、t a dog's details as a stri ngpublic Stri ng toStri ng()return super.toString() + "nit's " + name + " the " + breed; / A bark ing method public void soun d()System.out.pri ntln ("Woof Woof');/ Name of a Dog/ Dog breedprivate String name;private String breed; pack

7、age testabstract;public class Duck exte nds Ani malpublic Duck(Stri ng aName)super("Duck"); / Call the base con structor n ame = aName; / Supplied n ame breed = "Unknown" / Default breed valuepublic Duck(Stri ng aName, String aBreed)super("Duck"); / Call the base con st

8、ructor n ame = aName;/ Supplied n amebreed = aBreed; / Supplied breed/ Retur n a String full of a duck's detailspublic Stri ng toStri ng()return super.toString() + "nit's " + name + " the " + breed;/ A quack ing methodpublic void soun d()System.out.pri ntl n("Quack q

9、uackquack");private Stri ng n ame;/ Duck n ameprivate String breed; / Duck breed package testabstract;class Spaniel exte nds Dogpublic Spani el(Stri ng aName)super(aName, "Spa ni el");package testabstract;import java.util.Ra ndom;public class TestAbstractpublic static void main(String

10、 args)/ Create an array of three differe nt ani mals An imal theA ni mals = new Dog("Rover", "Poodle"),new Cat("Max", "Abyss in ia n"),new Duck("Dafy","Aylesbury"),new Spa ni el("Fido")；Ani mal petChoice;/ Choice of pet/ Ran dom n

11、u mberRandom select = new Random();gen erator/ Make five ran dom choices of petfor(i nt i = 0; i < 5; i+) / Choose a ran dom ani mal as a petpetChoice = theA nimalsselect. nextl nt(theA nimals .len gth);System.out.pri ntln ("nY our choice:n" + petChoice);petChoice.so un d();/ Get the pe

12、t'sreacti on2、接口接口可以被用來實現(xiàn)類間多繼承結(jié)構(gòu)。接口內(nèi)部只能定義public 的抽象方法和靜態(tài)的、公有常量，因此所有的方法需要在子類中實現(xiàn)。接口定義方法：訪問權(quán)限in terface接口名稱 exte nds 父接口名 1，父接口名2,./接口體程序范例 testinterface:package test in terface;public class Cat impleme nts PetOutputpublic Cat(Stri ng aName)super("Cat");/ Call the base con structorn ame =

13、 aName; / Supplied n amebreed = "Unknown" / Default breed valuepublic Cat(Stri ng aName, String aBreed)super("Cat");/ Call the base con structorn ame = aName;/ Supplied n amebreed = aBreed; / Supplied breed/ Return a String full of a cat's details public Stri ng toStri ng()re

14、tur n "n It's " + n ame + " the " + breed;/ A miaowi ng methodpublic void soun d()System.out.pri ntln ("Miiaooww");private String name; / Name of a catprivate String breed; / Cat breedpackage test in terface;public class Dog impleme nts PetOutputpublic Dog(Stri ng a

15、Name)n ame = aName;/ Supplied n amebreed = "Unknown" / Default breed valuepublic Dog(String aName, String aBreed) n ame = aName; / Supplied n ame breed = aBreed; / Supplied breed/ Prese nt a dog's details as a stri ngpublic Stri ng toStri ng()return "It's " + n ame + &quo

16、t; the " + breed;/ A bark ing methodpublic void soun d()System.out.pri ntln ("Woof Woof');public String getName()return n ame;private Stri ng n ame; / Name of a dogprivate String breed; / Dog breed package test in terface;public class Duck impleme nts PetOutputpublic Duck(Stri ng aName

17、)super("Duck"); / Call the base con structorn ame = aName;/ Supplied n amebreed = "Unknown" / Default breed valuepublic void layEgg()System.out.println("Egg laid");public Duck(Stri ng aName, String aBreed)super("Duck");/ Call the base con structorn ame = aName

18、;/ Supplied n amebreed = aBreed; / Supplied breed/ Retur n a String full of a duck's details public Stri ng toStri ng()retur n "n It's " + n ame + " the " + breed;/ A quack ing methodpublic void soun d()System.out.pri ntl n("Quack quackquack");private Stri ng n

19、ame; / Duck n ameprivate String breed; / Duck breedpackage test in terface;public in terface PetOutputvoid soun d();package test in terface;public in terface Read1void readNewspaper();package test in terface;/import testabstract.Read;class Spa niel exte nds Dog impleme nts Readl public Spani el(Stri

20、 ng aName)super(aName, "Spa ni el");public void readNewspaper( )System.out.pri ntl n("l can read Newspaper");package test in terface;import java.util.Ra ndom;public class Test In terfacepublic static void main(String args)/ PetOutput thePets = / Dog("Rover", "Poodle"),/new Cat("Max", "Abyss