抽象类实例

有若干个直柱体（底面与柱面垂直），其底面可能是圆形、矩形或三角形。
已知柱体的高度、圆的半径、矩形的宽度和高度及三角形的三边长（一定能构成三角形），计算柱体的体积和表面 （包括两个底的面积）

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner in=new Scanner(System.in);
Shape shape;
double volume = 0,Area = 0;
double height,a,b,c,width,length,radius;
char input;
while(in.hasNext()) {
input=in.next().charAt(0);
if(input=='C')
{
	height=in.nextDouble();
	radius=in.nextDouble();
	shape=new Circle(radius);
	Area=2*shape.area()+shape.perimeter()*height;
	volume=shape.area()*height;
}
if(input=='R')
{
	height=in.nextDouble();
	length=in.nextDouble();
	width=in.nextDouble();
	shape=new Rectangle(width,length);
	Area=2*shape.area()+shape.perimeter()*height;
	volume=shape.area()*height;
}
if(input=='T')
{
	height=in.nextDouble();
	a=in.nextDouble();
	b=in.nextDouble();
	c=in.nextDouble();
	shape=new Triangle(a,b,c);
	Area=2*shape.area()+shape.perimeter()*height;
	volume=shape.area()*height;
}
System.out.println(Area+" "+volume);
	}}

}
abstract class Shape//抽象图形父类
{
	public abstract double area();//抽象方法
	public abstract double perimeter();
}
class Circle extends Shape//子类圆
{
	private double radius;//半径
	
	public Circle(double radius)//构造方法
	{
		this.radius=radius;
	}
	public double area()//重写父类的抽象方法计算面积
	{
		return Math.PI*radius*radius;
	}
	public double perimeter()//重写父类的抽象方法计算周长
	{
		return 2*Math.PI*radius;
	}
}
class Rectangle extends Shape//子类矩形
{
	private double width,height;//矩形宽和高
	
	public Rectangle(double width,double height)//构造方法
	{
		this.width=width;
		this.height=height;
	}
	public double area()//重写父类的抽象方法计算面积
	{
		return width*height;
	}
	public double perimeter()//重写父类的抽象方法计算周长
	{
		return 2*(width+height);
	}
}
class Triangle extends Shape
{
	private double a,b,c;
	public Triangle(double a,double b,double c)
	{
		this.a=a;
		this.b=b;
		this.c=c;
	}
	public double area()
	{
		double p=(a+b+c)/2;
		return Math.sqrt((p-a)*(p-b)*(p-c));
	}
	public double perimeter() {
		
		return a+b+c;
	}
}