面向抽象编程和面向接口编程

原创

以下内容来自《Java 2实用教程》，主编：耿祥义、张跃平

鉴于面向抽象编程和面向接口编程思维培养的重要性，写此博客巩固。

面向抽象编程：

Circle.java

1 public class Circle { 2     double r; 3     Circle(double r){ 4         this.r=r; 5     } 6     public double getArea() { 7         return(3.14*r*r); 8     } 9 }

Pillar.java

 1 public class Pillar {  2     Circle bottom;    //bottom是用具体类Circle声明的对象  3     double height;  4     Pillar (Circle bottom,double height){  5         this.bottom=bottom;  6         this.height=height;  7     }  8     public double getVolume() {  9         return bottom.getArea()*height; 10     } 11 }

Geometry.java

1 public abstract class Geometry { 2     public abstract double getArea(); 3 }

Pillar.java

 1 public class Pillar {  2     Geometry bottom;    //bottom是抽象类Geometry声明的变量  3     double height;  4     Pillar (Geometry bottom,double height){  5         this.bottom=bottom;  6         this.height=height;  7     }  8     public double getVolume() {  9         if(bottom==null) { 10             System.out.println("没有底，无法计算体积"); 11             return -1; 12         } 13         return bottom.getArea()*height;    //bottom可以调用子类重写的getArea方法 14     } 15 }

Circle.java

1 public class Circle extends Geometry{ 2     double r; 3     Circle(double r){ 4         this.r=r; 5     } 6     public double getArea() { 7         return(3.14*r*r); 8     } 9 }

Rectangle.java

 1 public class Rectangle {  2     double a,b;  3     Rectangle(double a,double b){  4         this.a=a;  5         this.b=b;  6     }  7     public double getArea() {  8         return a*b;  9     } 10 }

Application.java

 1 public class Application {  2     public static void main(String args[]) {  3         Pillar pillar;  4         Geometry bottom=null;  5         pillar = new Pillar(bottom,100);    //null底的柱体  6         System.out.println("体积"+pillar.getVolume());  7         bottom=new Rectangle(12,22);  8         pillar=new Pillar(bottom,58);    //pillar是具有矩形底的柱体  9         System.out.println("体积"+pillar.getVolume()); 10         bottom=new Circle(10); 11         pillar =new Pillar (bottom,58);    //pillar是具有圆形底的柱体 12         System.out.println("体积"+pillar.getVolume()); 13     } 14 }

面向接口编程：

19:17:05

2018-07-07

文章来源: 面向抽象编程和面向接口编程

标签

面向接口编程

circle