Java-第06章-继承和多态8.30.ppt

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1、第6章继承和多态6.1何谓继承6.2继承语法细节6.1何谓继承什么时候用继承：多个类间出现重复的代码时，就把相同的代码提升为父类。如何在代码中体现继承：extends关键字publicclassSwordMan{privateStringname;//角色名称privateintlevel;//角色等级privateintblood;//角色血量publicvoidfight(){System.out.println("挥剑攻击");}publicintgetBlood(){returnblood;}publicvoidsetBlood(i

2、ntblood){this.blood=blood;}publicintgetLevel(){returnlevel;}publicvoidsetLevel(intlevel){this.level=level;}publicStringgetName(){returnname;}publicvoidsetName(Stringname){this.name=name;}}publicclassMagnician{privateStringname;//角色名称privateintlevel;//角色等级privateintblood;//

3、角色血量publicvoidfight(){System.out.println("魔法攻击");}publicintgetBlood(){returnblood;}publicvoidsetBlood(intblood){this.blood=blood;}publicintgetLevel(){returnlevel;}publicvoidsetLevel(intlevel){this.level=level;}publicStringgetName(){returnname;}publicvoidsetName(Stringname)

4、{this.name=name;}}publicclassRole{privateStringname;//角色名称privateintlevel;//角色等级privateintblood;//角色血量publicintgetBlood(){returnblood;}publicvoidsetBlood(intblood){this.blood=blood;}publicintgetLevel(){returnlevel;}publicvoidsetLevel(intlevel){this.level=level;}publicStrin

5、ggetName(){returnname;}publicvoidsetName(Stringname){this.name=name;}}Pullup扩充（extends）父类（继承）Java使用“extends”作为继承的关键词publicclassSwordManextendsRole{publicvoidfight(){System.out.println("挥剑攻击");}}编写主类，验证上述类之间的继承。publicclassRPG{publicstaticvoidmain(String[]args){SwordMansword

6、Man=newSwordMan();swordMan.setName("justin");swordMan.setLevel(1);swordMan.setBlood(200);System.out.printf("剑士：(%s,%d,%d)%n",swordMan.getName(),swordMan.getLevel(),swordMan.getBlood());Magicianmagician=newMagician();magician.setName("Monica");magician.setLevel(1);magician.

7、setBlood(100);System.out.printf("魔法师：(%s,%d,%d)%n",magician.getName(),magician.getLevel(),magician.getBlood());}}剑士：(justin,1,200)魔法师：(Monica,1,100)注意：父类的private成员会被继承，只是子类无法直接存取，必须通过父类提供的方法来存取。6.1.2多态与is-aJava继承的特点：子类只能继承一个父类。子类和父类是is-a关系。SwordmanisaRole,MagicialisaRole。这

8、是理解多态的基础SwordManswordMan=newSwordMan();Magicianmagician=newMagician();Rolerole1=newSwordM