java讲义面向对象程序设计Java

面向对象程序设计面向对象程序设计——June

MonaVajihollahiRoozbehFarahbod继承的概继承的概念：子类拥有父 classint intint intvoid voidvoid void intvoid}继承的概classStudent intvoid}继承的概Publicclasspublicstaticvoidmain(String[]Studentzhangsan=new}}继承的概Java 子类对象的创子类对象的创classint}}publicclassInher2extendsint//super();<-隐含}publicstaticvoidmain(String[]Inher2ob=newSystem.out.println(ob.a+"}}this与 super 的成员：age、heighteat()、sleep() this不 父类的构造函super(…)的位this与classint}Inher3_1(int}}publicclassInher3extendsintInher3(inta,int}publicstaticvoidmain(String[]Inher3ob=newInher3(10,System.out.println(ob.a+"}}继承中 控制classprivateintpublicvoidsetA(int}intreturn}}publicclassInher4extendsvoid}publicstaticvoidmain(String[]Inher4ob=new}}覆成员变量的覆盖：变量名相成员方法的覆盖：返回值类型、方法名、形式参数都相正确：private->public,default错误：public->private,public不 overload与8.5覆成员变量覆盖(意义不大classint}publicclassInher5extendsintvoid}publicstaticvoidmain(String[]Inher5ob=new}}8.5覆成员方法覆class }}publicclassInher6extends System.out.println("高兴}publicstaticvoidmain(String[]Inher6ob=new }}8.5覆class }}publicclassInher7extends o(String}publicstaticvoidmain(String[]Inher7ob=new }}8.5覆super用 当前对象的父父类被隐藏的成员变量，如8.5覆classSuperClass{intx;SuperClass(){System.out.println(“inSuperClass x=“}voiddoSomething()}}8.5覆classSubClassextendsSuperClass{intx;SubClass()super( //callconstructorof //superSystem.out.println(“inSubClass}voiddoSomething()super.doSomething();//callmethodof8.5覆}}publicclassinheritancepublicstaticvoidmain(Stringargs[]){SubClasssubC=newSubClass();}}8.5覆运行结c:\>javainheritanceinSuperClass:x=3inSubClass: ininSubClass.doSomething()super.x=3sub.x=58.6多由方法重载(overload)子类对象可以作为父类对象使用。在程序中凡是需要父对象的地方，都可以用子类对象代由方法覆盖(override)实调用规则：根据实例的类型决定调用的方8.9ObjectObject类是所有类的父Object类常用方8.10与•==一般用于基本数据类型的比较，用于 Strings1=newStrings2=new8.9与StringString8.10与equals()用于比较对象的内Strings1=newStrings2=new8.10与Object类的equals()方法定义publicbooleanequals(Objectreturn}8.10与注8.11Object 变Object 变量可以用 所有的变publicclasspublicstaticvoidmain(String[]Object[]ob=newob[0]=newob[1]=newob[2]=newfor(int}}8.11Object 变判断对象类型publicclasspublicstaticvoidmain(String[]Objectob[]=newob[0]=newob[1]=newob[2]=newfor(intif(ob[i]instanceofString}elseif(ob[i]instanceofBooleanbooleanSystem.out.println(b2&&}}}}8.12类的层级AADDCB8.12类的层级classintSystem.out.println("执行A的构造函数}}classBextendsintSystem.out.println("执行B的构造函数}}