抽象类与接口的应用

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1、.一个类永远不要去继承一个已经实现好的类，而只能继承抽象类或实现接口范例：为抽象类实例化abstractclassA{                        //定义抽象类A      publicabstractvoidprint();  //定义抽象方法print()}classBextendsA{                      //子类继承抽象类      publicvoidprint(){             System.out.println("Helloworld!");      }}publicclassAbstractCaseD

2、emo01{      publicstaticvoidmain(Stringargs[]){             Aa=newB();                    //通过子类为抽象类实例化             a.print();                      //调用的方法是被子类覆写过的方法      }}范例：为接口实例化interface A{                     //定义接口A      publicvoidprint(); //定义抽象方法print()}classBimplementsA{         

3、       //子类实现接口      publicvoidprint(){             System.out.println("Helloworld!");      }}publicclassInterfaceCaseDemo01{      publicstaticvoidmain(Stringargs[]){             Aa=newB();                    //通过子类为抽象类实例化             a.print();                      //调用的方法是被子类覆写过的方法      

4、}}抽象类的实际应用-->模板设计范例：抽象类的实际应用abstractclassPerson{                       //定义抽象类Person      privateStringname;                    //定义name属性      privateintage;                           //定义age属性      publicPerson(Stringname,intage){           //为属性初始化             this.name=name;           

5、                  //为name属性赋值             this.age=age;                                   //为age属性赋值      }      publicStringgetName(){                          //取得name属性内容             returnname;      }      publicintgetAge(){                                  //取得age属性内容             retu

6、rnage;      }      publicvoidsay(){                                     //说话是具体功能，要定义成普通方法             System.out.println(this.getContent());      }      publicabstractStringgetContent();     //说话内容由子类定义}classStudentextendsPerson{                          //定义Student继承Person类      privatef

7、loatscore;                                   publicStudent(Stringname,intage,floatscore){             super(name,age);                               //调用父类中构造方法             this.score=score;              }      publicStringgetContent(){