【Java每日一题】——第三十六题：设计一个长方形类Rectangle和它的3个子类：圆类Circle、圆球体类Sphere和圆柱体类Cylinder，分别求它们的面积

package file3;
class Rectangle{
  private double x;
  private double y;
  public Rectangle() {
    super();
  }
  public Rectangle(double x) {
    super();
    this.x = x;
  }
  public Rectangle(double x, double y) {
    super();
    this.x = x;
    this.y = y;
  }
  public double getX() {
    return x;
  }
  public void setX(double x) {
    this.x = x;
  }
  public double getY() {
    return y;
  }
  public void setY(double y) {
    this.y = y;
  }
  public double area(){
    return x*y;
  }
  @Override
  public String toString() {
    return  "长方形的长：" + getX() + " 长方形的宽：" + getY() + " 表面积：" + area();
  }
}
 
class Circle extends Rectangle{
  public Circle (){
    super();
  }
 
  public Circle(double x) {
    super(x);
  }
  @Override
  public double area() {
    // TODO Auto-generated method stub
    return getX()*getX()*3.1615926;
  }
 
  @Override
  public String toString() {
    return "圆的半径为："+getX()+" 面积为："+area();
  }
}
class Sphere extends Rectangle{
 
  public Sphere() {
    super();
  }
 
  public Sphere(double x) {
    super(x);
  }
  @Override
  public double area() {
    // TODO Auto-generated method stub
    return 4*3.1415926*getX()*getX();
  }
 
  @Override
  public String toString() {
    return "球的半径：" + getX()+" 表面积为:"+area();
  }
}
class Cylinder extends Rectangle{
 
  public Cylinder() {
    super();
    // TODO Auto-generated constructor stub
  }
 
  public Cylinder(double x, double y) {
    super(x, y);
    // TODO Auto-generated constructor stub
  }
  @Override
  public double area() {
    // TODO Auto-generated method stub
    return getX()*getX()*3.1415926*2+getX()*2*3.1415926*getY();
  }
  @Override
  public String toString() {
    return "圆柱的底面半径为:"+getX()+" 高为："+getY()+" 表面积为"+area();
  }
}
public class Demo {
  public static void main(String[] args) {
    // TODO Auto-generated method stub
    Rectangle r1=new Rectangle(2.4,5.6);
    System.out.println(r1.toString());
    Circle c1=new Circle(3.0);
    System.out.println(c1.toString());
    Sphere s1=new Sphere(3.0);
    System.out.println(s1.toString());
    Cylinder c2=new Cylinder(3.0, 5.0);
    System.out.println(c2.toString());
  }
 
}