类的抽象与封装

 import java.util.Scanner; class Circle

{   private double radius;//存放圆的半径 public double getRadius() {//获取半径 return radius; } public void setRadius(double radius) { this.radius = radius; }

public Circle(){ this.radius=0; }

public Circle(double r ){ this.radius=r; }

public double getArea(){ double r=this.radius; double area=r*r*3.14; return area; }

public double getPerimeter(){ double perimeter=this.radius*2*3.14; return perimeter; }

public void show()

{ System.out.println("请输入圆的半径");

Scanner scanner = new Scanner(System.in);

Scannerthis.setRadius(scanner.nextInt());

System.out.println("圆的半径"+this.getRadius());

System.out.println("圆的周长"+this.getPerimeter());

System.out.println("圆的面积"+this.getArea()); } }

 class Cylinder extends Circle {

private double height;

public double getHeight() { return height; }

public void setHeight(double height) { this.height = height; }

  public Cylinder (double r, double  h){ this.height=h; this.setRadius(r); }

public double getVolume( )

{ double volume=this.getArea()*this.height;//圆柱体的体积公式 return volume; }

public void showVolume()

{ System.out.println("圆柱的体积"+this.getVolume()); } }  

 public class Test {  public static void main(String[] args) {  Circle circle=new Circle();  circle.show();

 Cylinder cylinder=new Cylinder(2,4); 

 cylinder.showVolume();  }  }