13，学习多态

参数都是Pet类的子类
可否使用一个feed(Pet pet)实现对所有宠物的喂食？

使用多态实现思路

• 编写父类
• 编写子类，子类重写父类方法
• 运行时，使用父类的类型，子类的对象
  Pet pet = new Dog();

使用父类作为方法形参实现多态

public class Master {
//使用父类作为方法形参 
    public void feed( Pet pet ) {
           pet.eat();         
    }
}

Pet pet = new Dog();
Master master = new Master();
master.feed( pet );//同一种操作方式，不同的操作对象 

习题示例

public abstract class MotoVehicle {
    private String no;//车牌号
    private String brand;//品牌

    abstract int calRent(int days);//计算租金

    public MotoVehicle()
    {

    }
    public MotoVehicle(String no, String brand)
    {
        this.no = no;
        this.brand = brand;
    }

    public String getNo() {
        return no;
    }

    public void setNo(String no) {
        this.no = no;
    }

    public String getBrand() {
        return brand;
    }

    public void setBrand(String brand) {
        this.brand = brand;
    }
}

public class Car extends MotoVehicle{


    public Car(String no, String brand)
    {
        super(no,brand);

    }
    @Override
    int calRent(int days) {
        if(getBrand().equals("宝马"))
        {
            return 500 * days;
        }
        else
        {
            return 600 * days;
        }

    }
}

public class Kache extends MotoVehicle {
    private int dunwei;//吨位

    public Kache(int dunwei)
    {
        this.dunwei = dunwei;
    }

    @Override
    int calRent(int days) {
        return 50*dunwei*days;
    }
}

不用多态的实现方式

Car[] cars = new Car[3];
        cars[0] = new Car("辽A12345","宝马");
        cars[1] = new Car("辽B22222","别克");
        cars[2] = new Car("辽A62222","奔驰");

        Kache[] kaches = new Kache[2];
        kaches[0] = new Kache(1);//150
        kaches[1] = new Kache(4);//600

        int total = 0;
        for(int i = 0; i < cars.length; i++)
        {
            total += cars[i].calRent(3);
        }
        for(int i = 0; i < kaches.length; i++)
        {
            total += kaches[i].calRent(3);
        }


        System.out.println("总租金" + total);//5850

使用多态实现

MotoVehicle[] motoVehicles = new MotoVehicle[5];
        motoVehicles[0] = new Car("辽A12345","宝马");
        motoVehicles[1] = new Car("辽B22222","别克");
        motoVehicles[2] = new Car("辽A62222","奔驰");
        motoVehicles[3] = new Kache(1);
        motoVehicles[4] = new Kache(4);
        int total = 0;
        for(int i = 0; i < motoVehicles.length; i++)
        {
            total += motoVehicles[i].calRent(3);
        }

        System.out.println("总租金" + total);

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作者：豆约翰
链接：https://www.jianshu.com/p/3bacbcb9bdec
來源：
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