C#程序设计实验--抽象类和派生类

问题

使用抽象类实现shape，抽象类包含两个接口面积和周长。并用virtual和override实现rectangle和square类

解析

1 如图存在两种实现，

（ 1）长方形与正方形直接派生

（2） 正方形派生长方形， 长方形派生Shape

(2)的设计要比(1)更好，因为它是对真实世界的反映，代码更简洁。

2、创建抽象类Shape

abstract class Shape
    {
        public abstract double Perimeter();
        public abstract double Area();
    }

3、实现派生类Rectangle

class Rectangle : Shape
    {
        protected double length;
        protected double width;

        public Rectangle(double length, double width)
        {
            this.length = length;
            this.width = width;
        }

        public Rectangle(double a)
        {
            this.length = this.width = a;
        }

        public Rectangle()
        {
            this.length = this.width = 0;
        }

        public override double Perimeter()
        {
            return (this.length + this.width) * 2;
        }

        public override double Area()
        {
            return this.length * this.width;
        }
    }

4、实现派生类Square

class Square : Rectangle
    {
        public Square(double a)
        {
            this.length = this.width = a;
        }
    }

注意

Rectangle需要提供一个默认构造函数和含一个参数的构造函数，这是因为Square的构造函数需要。

完整控制台程序如下：

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

namespace Shape
{
    abstract class Shape
    {
        public abstract double Perimeter();
        public abstract double Area();
    }

    class Rectangle : Shape
    {
        protected double length;
        protected double width;

        public Rectangle(double length, double width)
        {
            this.length = length;
            this.width = width;
        }

        public Rectangle(double a)
        {
            this.length = this.width = a;
        }

        public Rectangle()
        {
            this.length = this.width = 0;
        }

        public override double Perimeter()
        {
            return (this.length + this.width) * 2;
        }

        public override double Area()
        {
            return this.length * this.width;
        }
    }

    class Square : Rectangle
    {
        public Square(double a)
        {
            this.length = this.width = a;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Square s = new Square(12);
            Console.WriteLine("面积为："+s.Area());
        }
    }
}

5.、完成界面

总结

采用抽象类和派生类是面向对象设计的核心，设计关键在于分析类间的关系和接口。合理的设计能够大大简化编码量，便于日后维护和重用。