java面向抽象编程样例

import java.util.*;
abstract class Geometry{
public abstract double getArea();

}
class Pillar{
Geometry bottom;
double height;
Pillar(Geometry bottom ,double height){
this.bottom=bottom;
this.height=height;

}
public double getVolume(){
return bottom.getArea()*height;
}
}

class Circle extends Geometry{
double r;
Circle(double r){

this.r=r;

}
public double getArea(){
return(3.14*r*r);
}
}

class Rectangle extends Geometry{
double a,b;
Rectangle(double a,double b){

this.a=a;
this.b=b;
}
public double getArea(){
return(a*b);
}
}

public class Main {
public static void main(String args[]){
Pillar pillar;
Geometry bottom;
bottom =new Rectangle(12,22);
pillar=new Pillar(bottom,58);
System.out.println("矩形的面积"+pillar.getVolume());

bottom=new Circle(10);
pillar=new Pillar(bottom,58);
System.out.println("圆柱的体积"+pillar.getVolume());
}
}