packagecom.bdqn;publicclassMaster{publicvoidplayWithPet(Petpet){if(petinstanceofDog){Dogdog=(Dog)pet;dog.play();}elseif(petinstanceofPenguin){Penguinpenguin=(Penguin)pet;penguin.play();}}}Pet类代码：
packagecom.bdqn;publicabstractclassPet{privateStringname;privateinthealth;privateintlove;publicvoidsetName(Stringname){this.name=name;}publicStringgetName(){returnname;}publicvoidsetHealth(inthealth){if(health<0||health>100){health=60;}this.health=health;}publicintgetHealth(){returnhealth;}publicvoidsetLove(intlove){if(love<0||love>100){love=60;}this.love=love;}publicintgetLove(){returnlove;}publicvoidprint(){System.out.println("宠物的自白：");System.out.print("我的名字叫"+getName()+"，健康值是"+getHealth()+"，和主人的亲密度是"+getLove());}publicabstractvoidplay();}Dog类代码：
packagecom.bdqn;publicclassDogextendsPet{privateStringstrain;publicStringgetStrain(){returnstrain;}publicvoidsetStrain(intstrain){if(strain==1){this.strain="拉布拉多";return;}this.strain="博美";}publicvoidprint(){super.print();System.out.println(",我的种类是："+this.getStrain());}publicvoidplay(){System.out.println("扔飞碟出去，狗狗跑去捡回来......");}publicvoidtoHospital(){System.out.println("打针、吃药");super.setHealth(60);}}Penguin类代码：
packagecom.bdqn;publicclassPenguinextendsPet{privateStringsex;publicStringgetSex(){returnsex;}publicvoidsetSex(intsex){if(sex==1){this.sex="Q仔";return;}this.sex="Q妹";}publicvoidprint(){super.print();System.out.println("，我的性别是："+this.getSex());}publicvoidplay(){System.out.println("带企鹅去南极游泳......");}}