解析java多态经典习题

1 题目一

1.1 题目内容

编写程序实现乐手弹奏乐器。乐手可以弹奏不同的乐器从
而发出不同的声音。
可以弹奏的乐器包括二胡、钢琴和琵琶。
实现思路及关键代码：
①定义乐器类Instrument，包括方法makeSound()
②定义乐器类的子类：二胡Erhu、钢琴Piano和
小提琴Violin
③定义乐手类Musician，可以弹奏各种乐器
play(Instrument i)
④定义测试类,给乐手不同的乐器让他弹奏

1.2 示例代码

Instrument类

package Work03;
public class Instrument {public void makeSound(){System.out.println("乐器在奏乐");}
}

Erhu类

package Work03;public class Erhu extends Instrument{@Overridepublic void makeSound() {System.out.println("二胡,弹奏的曲目是二泉映月");}
}

Piano类

package Work03;public class Piano extends Instrument{@Overridepublic void makeSound() {System.out.println("钢琴,弹奏的曲目是致爱丽丝");}
}

Violin类

package Work03;public class Violin extends Instrument{@Overridepublic void makeSound() {System.out.println("小提琴,弹奏的曲目是沉思");}
}

Muscian类

package Work03;public class Musician {private String  name;public Musician() {}public Musician(String name) {this.name = name;}public void play(Instrument i){System.out.print(name+"弹奏的乐器是");i.makeSound();}
}

Test类

package Work03;
public class Test {public static void main(String[] args) {Musician m=new Musician("张三");m.play(new Piano());m.play(new Erhu());m.play(new Violin());}
}

1.3 示例代码运行截图

在这里插入图片描述

2 题目二

2.1 题目内容

编写程序实现主人喂养宠物和跟宠物玩耍的场景
定义宠物类Pet，宠物都需要吃东西,跟主人玩。
定义狗类Dog、猫类Cat、Dolphin海豚类继承Pet宠物类。
狗狗吃骨头、猫咪吃老鼠、海豚吃乌贼。

主人和宠物的玩耍是每个宠物都独有一份

主人跟狗狗完抓飞盘，主人跟猫咪玩抓老鼠、主人跟海豚玩转圈圈。

2.2 示例代码

Pet类

package Work03;
//上课练习
public class Pet {private String name;public Pet() {}public Pet(String name) {this.name = name;}//吃的方法public void eat(){}public String getName() {return name;}public void setName(String name) {this.name = name;}
}

Dog类

package Work03;public class Dog extends Pet{public Dog() {}public Dog(String name) {super(name);}public void catchDisc() {System.out.println("玩抓飞盘");}@Overridepublic void eat() {System.out.println("狗狗在啃骨头");}
}

Cat类

package Work03;public class Cat extends Pet{public Cat() {}public Cat(String name) {super(name);}public void catchMouse() {System.out.println("玩抓老鼠");}@Overridepublic void eat() {System.out.println("猫咪吃老鼠");}
}

Dolphin类

package Work03;public class Dolphin extends Pet{public Dolphin() {}public Dolphin(String name) {super(name);}public void runningCircle() {System.out.println("玩转圈圈");}@Overridepublic void eat() {System.out.println("海豚吃乌贼");}
}

Master类

package Work03;public class Master {private  String name;public Master() {}public Master(String name) {this.name = name;}public void feed(Pet pet){//得出喂食的宠物是什么名字,是狗还是猫还是海豚if(pet instanceof Dog){System.out.println(name+"喂食的宠物是一只叫"+ ((Dog)pet).getName()+"的狗狗");}else if(pet instanceof Cat){System.out.println(name+"喂食的宠物是一只叫"+ ((Cat)pet).getName()+"的猫咪");}else if(pet instanceof Dolphin){System.out.println(name+"喂食的宠物是一只叫"+ ((Dolphin)pet).getName()+"的海豚");}//吃的方法都是被重写的,无需进行类型的判断pet.eat();}public void play(Pet pet){//每个宠物的玩耍方法都是其独有的方法,因此需要向下转型,向下转型前需要对类型进行判断if(pet instanceof Dog){System.out.print(name+"是和一只叫"+ ((Dog)pet).getName()+"的狗狗");((Dog)pet).catchDisc();}else if(pet instanceof Cat){System.out.print(name+"是和一只叫"+ ((Cat)pet).getName()+"的猫咪");((Cat)pet).catchMouse();}else if(pet instanceof Dolphin){System.out.print(name+"是和一只叫"+ ((Dolphin)pet).getName()+"的海豚");((Dolphin)pet).runningCircle();}}
}

Test类

package Work03;
public class Test {public static void main(String[] args) {Master master=new Master("张三");Dog dog=new Dog("德福");Cat cat=new Cat("叮当");Dolphin dolphin=new Dolphin("祥云");master.feed(dog);master.feed(cat);master.feed(dolphin);master.play(dog);master.play(cat);master.play(dolphin);}
}