定义一个抽象类shape,它包含一个抽象方法getArea()

定义一个抽象类Shape,它包含一个抽象方法getArea()，从Shape类派生出Rectangle和Circle类，这两个类都用getArea()方法计算对象面积，编写应用程序使用Rectangle和Circle类。

实验目的：定义Rectangle和Circle类的构造方法，初始化成员变量，并计算出面积。

代码如下（示例）：

package com.ljc.Abstract;

//创建了Shape抽象类
abstract class Shape {

	//写抽象方法getArea
	abstract double getArea();
}


	//继承Shape抽象类派生出Rectangle类
class Rectangle extends Shape {
	double a, b;
	
	//构造方法
	Rectangle() {
	}
	//初始化变量
	Rectangle(double a, double b) {
		this.a = a;
		this.b = b;
	}
	//输入方法
	double getA(double a) {
		this.a = a;
		return a;
	}
	//输入方法
	double getB(double b) {
		this.b = b;
		return b;
	}
	//输出方法，抽象方法调用
	double getArea() {
		return (a * b) / 2;
	}
}


//解释同上
class Circle extends Shape {
	double r;

	Circle() {
	}

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

	double getR(double r) {
		this.r=r;
		return r;
	}
	//使用调用Java库使用math方法，把Π的值调出来
	double getArea() {
		return r*r*Math.PI;
	}
}

package com.ljc.Abstract;

public class ShapeTest {

	public static void main(String[] args) {
	
	//测试方法就不过多介绍
		Rectangle a=new Rectangle();
		a.getA(60.4);
		a.getB(35.1);
		System.out.println(a.getArea());
		Circle b=new Circle();
		b.getR(3);
		System.out.println(b.getArea());
	}

}

class Shape:
    def __init__(self,areas=0,primeters=0):
       self.areas=areas
       self.Primeters=primeters
    def GetPrimeter(self):
        pass
    def GetArea(self):
       pass
class Triangle(Shape):
    def __init__(self,said1=0,said2=0,said3=0,areas=0,primeters=0):
        super().__init__(areas,primeters)
        self.said1=said1
        self.said2=said2
        self.said3=said3
    def GetPrimeter(self):
        self.Primeters=(self.said1+self.said2+self.said3)
    def GetArea(self):
        s = (self.said1 + self.said2 + self.said3) / 2
        self.areas = ((s * (s - self.said1)) * (s - self.said2) * (s - self.said3))**0.5
class Rectangle(Shape):
    def __init__(self,length=0,width=0,areas=0,primeters=0):
        super().__init__(areas,primeters)
        self.length=length
        self.width=width
    def GetPrimeter(self):
        self.Primeters=(self.length+self.width)*2
    def GetArea(self):
        self.areas=self.length*self.width
class Circle(Shape):
    def __init__(self,r=0,areas=0,primeters=0):
        super().__init__(areas,primeters)
        self.r=r
    def GetPrimeter(self):
        self.Primeters=2*3.14*self.r
    def GetArea(self):
        self.areas=3.14*self.r*self.r
a1=Triangle(3,4,5)
a1.GetPrimeter()
a1.GetArea()
print("三角形的周长为：",a1.Primeters)
print("三角形的面积为：",a1.areas)

a2=Rectangle(4,5)
a2.GetPrimeter()
a2.GetArea()
print("矩形的周长为：",a2.Primeters)
print("矩形的面积为：",a2.areas)

a3=Circle(4)
a3.GetPrimeter()
a3.GetArea()
print("圆的周长为：",a3.Primeters)
print("圆的面积为：",a3.areas)