类的抽象与封装

//圆类

package lx;

public class Circle {
 private double Radius;//存放圆的半径
 public double getRadius() {//获取圆的半径
  return Radius;
 }
 public void setRadius(double radius) {//设定半径
  Radius = radius;
 }
 public Circle( ){//无参构造函数，将半径设为0
  this.Radius=0;
 }
 public Circle(double  r){//带参构造函数，将半径初始化为r
  this.Radius = r;
 }
 public double getArea(double r){//获取圆的面积
  return 3.14159 * r * r;
 }
 public double getPerimeter(double r){//获取圆的周长
  return 2 * 3.14159* r;
 }
 public void  show( ){
  System.out.println("圆的面积： " + this.getArea(Radius));
  System.out.println("圆的周长： " + this.getPerimeter(Radius));
 }

}

 

//圆柱类
public class Cylinder extends Circle {//在圆的基础上定义一个圆柱
 private double hight;
   public Cylinder (double r, double  h ){
   super(r);
   this.hight = h;
  }
  public double getVolume(){//求圆柱的体积
   return 3.14159 * this.getRadius() * this.getRadius() * hight;
  }  
  public void showVolume( ){
   System.out.println("圆柱体的体积：" + this.getVolume());
  }
}
public class Test {
  public static void main(String[] args) {
  Circle cc = new Circle();
  cc.show( );
  Cylinder ccc =new Cylinder(3, 6);//圆柱的底面圆的半径和和圆柱的高
  ccc.showVolume();

 }

}