Question

设计一个Shape接口和它的两个实现类Square和Circle 要求：Shape接口中有一个抽象方法area()，

设计一个Shape接口和它的两个实现类Square和Circle 要求：Shape接口中有一个抽象方法area()，方法接收一个double类型的参数，返回一个double类型的结果，Square和Circle中实现Shape接口的area()抽象方法，分别求正方形和圆形的面积并返回，在测试类中创建Square和Circle对象，计算边长为2的正方形面积和半径为3的圆形面积

Answer 1

#include<iostream>

using namespace std;

class Shape
{
public:
    virtual double Area(double length){}
};

class Square:Shape
{
public:
    double Area(double length){cout<<"Square::Area()=";return length*length;}
};

class Circle:Shape
{
public:
    double Area(double length){cout<<"Circle::Area()=";return 3.14*length*length;}
};

//这里体现了多态使用，接受CShape类型的指针，添加新的子类不用更改该函数，提高扩展性
void test(Shape  *shape,double length)
{
    cout<<shape->Area( length )<<endl;
}

int main()
{
    Square         s;
    Circle      c;
    //边长为2的正方形面积
    test( &s , 2 );
    //半径为3的圆形面积
    test( &c , 3 );
}

Answer 2

你这个是黑马教材的第四章编程第二题吧
interface Shape { double area(double givenValue); } class Square implements Shape{ public double area(double sideLength)
{ return sideLength*sideLength; } } class Circle implements Shape{ public double area(double r) { return Math.PI*r*r; } } public class
Test02 { public static void main(String[] args) { Shape square = new Square(); Shape circle = new Circle();
System.out.println(square.area(2)); System.out.println(circle.area(3)); } }

Answer 3

class Program
{
static void Main(stringI args)
Square sq : new Square() ;
Circle ci : new Circle() ;
Console. WriteLine("正方形的面积为："+ sq.Area(2));
Console. WriteLine（"圆形的面积为："+ ci. Area(3));
Console. ReadKey() ;
}
}
}
interface Shape
double Area(double r);
}
class Square : Shape
{
public double Area (double r)l
{return*r}
}
class Circle : Shape
{
public double Area(double r)
{
return Math.PI* r * r;
}
}