java学习日志（三）---实验2

题目：(1)编写一抽象类（shape），长方形类、三角形类与圆类均为其子类，并各有各的属性。其中父类有获得其周长、面积的方法。然后在一测试类中，分别建立若干个子对象，并分别将这些对象的面积与周长统计输出。

(2)在上述基础上，编写锥体，包括下底和高，求下底分别为长方形，三角形，圆形的椎体体积。

public abstract class Shape
{
public abstract double getPerimeter();
public abstract double getArea();
}

public class Rectangle extends Shape
{
double a,b;
Rectangle(double a,double b){
this.a=a;
this.b=b;
}
public double getPerimeter(){
return 2*a*b;
}
public double getArea(){
return a*b;
}
}

public class Circle extends Shape
{
double r;
Circle(double r){
this.r=r;
}
public double getPerimeter(){
return 2*3.14*r;
}
public double getArea(){
return 3.12*r*r;
}
}

import java.lang.Math;

public class Triangle extends Shape
{
double a,b,c,d;
Triangle(double a,double b,double c){
this.a=a;
this.b=b;
this.c=c;
}
public double getPerimeter(){
return a+b+c;
}
public double getArea(){
return Math.sqrt(a*a+b*b)*c*0.5;
}
}

public class Pyramis
{
Shape bottom;
double height;
Pyramis(Shape bottom,double height){
this.bottom=bottom;
this.height=height;
}
public double getVolume(){
return bottom.getArea()*height*1/3;
}
}

public class Application
{
public static void main(String[] args)
{
Pyramis pyramis;
Shape shape1=new Rectangle(3,4);
pyramis=new Pyramis(shape1,3);
System.out.println("矩形的周长为："+shape1.getPerimeter());
System.out.println("矩形的面积为："+shape1.getArea());
System.out.println("四棱锥的体积为："+pyramis.getVolume());
System.out.println();

Shape shape2=new Circle(4);
pyramis=new Pyramis(shape2,3);
System.out.println("圆的周长为："+shape2.getPerimeter());
System.out.println("圆的面积为："+shape2.getArea());
System.out.println("圆锥的体积为："+pyramis.getVolume());
System.out.println();

Shape shape3=new Triangle(3,4,5);
pyramis=new Pyramis(shape3,3);
System.out.println("三角形的周长为："+shape3.getPerimeter());
System.out.println("三角形的面积为："+shape3.getArea());
System.out.println("三角锥的体积为："+pyramis.getVolume());
System.out.println();
}
}