Chapter 8. 面向对象（多态--抽象类）-优快云博客

本文通过具体的C#代码示例介绍了抽象类和多态的概念。首先定义了抽象类Animal及其抽象方法Bark()，并通过派生类dog和cat实现不同动物叫声的具体行为。随后介绍了形状抽象类Shape及其抽象方法GetArea()和GetPerimeter()，并展示了如何通过Circle和Square类实现计算圆形和矩形的面积与周长。

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace 抽象类
{
    class Program
    {
        static void Main(string[] args)
        {
            //狗狗会叫，猫咪也会叫
            Animal a = new dog();
            a.Bark();
            Console.ReadLine();
　　　　　　  

            Animal aa = new cat();
            aa.Bark();
            Console.ReadLine();
　　　　　　　　//使用多态求矩形和圆形的面积和周长
            Shape shape = new Circle(5);
            double area = shape.GetArea();
            double perimeter = shape.GetPerimeter();
            Console.WriteLine("面积是{0}，周长是{1}", area, perimeter);
            Console.ReadLine();
　　　　　　　　

            Shape shape1 = new Square(10,20);
            double area1 = shape1.GetArea();
            double perimeter1 = shape1.GetPerimeter();
            Console.WriteLine("面积是{0}，周长是{1}",area1,perimeter1);
            Console.ReadLine();
　　　　　　　　
        }



        public abstract class Animal       //抽象类
        {
            public abstract void Bark();    //抽象方法
        }

        public class dog : Animal
        {
            public override void Bark()
            {
                Console.WriteLine("狗狗旺旺的叫");
            }
        }

        public class cat : Animal
        {
            public override void Bark()
            {
                Console.WriteLine("猫咪喵喵的叫");
            }
        }


        public abstract class Shape       //抽象类
        {
            public abstract double GetArea();       //抽象方法
            public abstract double GetPerimeter();
        }

        public class Circle : Shape　　//圆形类
        {
            private double _r;

            public double R
            {
                get { return _r; }
                set { _r = value; }
            }

            public Circle(double r)
            {
                this.R = r;
            }

            public override double GetArea()
            {
                return Math.PI * this.R * this.R;
            }

            public override double GetPerimeter()
            {
                return 2 * Math.PI * this.R;
            }
        }

        public class Square : Shape     //矩形类
        {
            private double _height;

            public double Height
            {
                get { return _height; }
                set { _height = value; }
            }

            private double _width;

            public double Width
            {
                get { return _width; }
                set { _width = value; }
            }

            public Square(double height, double width)
            {
                this.Height = height;
                this.Width = width;
            }



            public override double GetArea()
            {
                return this.Height * this.Width;
            }

            public override double GetPerimeter()
            {
                return 2 * (this.Height + this.Width);
            }
        }
    }
}