Java 父类和子类 

 1 package chapter11;
 2 
 3 public class GeometricObject1 {
 4     private String color="white";
 5     private boolean filled;
 6     private java.util.Date dateCreated;
 7     
 8     public GeometricObject1(){
 9         dateCreated=new java.util.Date();
10     }
11     
12     public GeometricObject1(String color, boolean filled){
13         dateCreated=new java.util.Date();
14         this.color=color;
15         this.filled=filled;
16     }
17     
18     public String getColor(){
19         return color;
20     }
21     public void setColor(String color){
22         this.color=color;
23     }
24     
25     public boolean isFilled(){
26         return filled;
27     }
28     public void setFilled(boolean filled){
29         this.filled=filled;
30     }
31     
32     public java.util.Date getDateCreated(){
33         return dateCreated;
34     }
35     
36     public String toString(){
37         return "created on "+dateCreated+"\ncolor: "+color+" and filled: "+filled;
38     }
39 
40 }

首先新建一个几何体类，作为父类，具有一般几何体的共性；

 1 package chapter11;
 2 
 3 public class Circle4 extends GeometricObject1 {
 4     private double radius;
 5     public Circle4(){
 6         
 7     }
 8     public Circle4(double radius){
 9         this.radius=radius;
10     }
11     public Circle4(double radius,String color,boolean filled){
12         this.radius=radius;
13         setColor(color);
14         setFilled(filled);
15     }
16     
17     public double getRadius(){
18         return radius;
19     }
20     public void setRadius(double radius){
21         this.radius=radius;
22     }
23     
24     public double getArea(){
25         return radius*radius*Math.PI;
26     }
27     public double getDiameter(){
28         return 2*radius;
29     }
30     public double getPerimeter(){
31         return 2*radius*Math.PI;
32     }
33     public void printCircle(){
34         System.out.println("The circle is created "+getDateCreated()+
35                 " and the radius is "+radius);
36     }
37 
38 }
 1 package chapter11;
 2 
 3 public class Rectangle1 extends GeometricObject1 {
 4     private double width;
 5     private double height;
 6     
 7     public Rectangle1(){
 8         
 9     }
10     public Rectangle1(double width,double height){
11         this.width=width;
12         this.height=height;
13     }
14     public Rectangle1(double width,double height,String color,boolean filled){
15         this.width=width;
16         this.height=height;
17         setColor(color);
18         setFilled(filled);
19     }
20     
21     public double getWidth(){
22         return width;
23     }
24     public void setWidth(double width){
25         this.width=width;
26     }
27     
28     public double getHeight(){
29         return height;
30     }
31     public void setHeight(double height){
32         this.height=height;
33     }
34     
35     public double getArea(){
36         return width*height;
37     }
38     public double getPerimeter(){
39         return 2*(width+height);
40     }
41     
42 
43 }

然后建立了基于父类的两个子类，Circle和Rectangle类，分别具有自己的数据域和方法属性，并实现。

 1 package chapter11;
 2 
 3 public class TestCircleRectangle {
 4 
 5     public static void main(String[] args) {
 6         // TODO Auto-generated method stub
 7         Circle4 circle=new Circle4(1);
 8         System.out.println("A circle "+circle.toString());
 9         System.out.println("The radius is "+circle.getRadius());
10         System.out.println("The area is "+circle.getArea());
11         System.out.println("The diameter is "+circle.getDiameter());
12         
13         Rectangle1 rectangle=new Rectangle1(2,4);
14         System.out.println("\nA rectangle "+rectangle.toString()+"\nThe area is "+
15         rectangle.getArea()+"\nThe perimeter is "+rectangle.getPerimeter());
16 
17     }
18 
19 }

这是对子类的测试。

总结：

1、子类并不是父类的一个子集，实际上，一个子类通常比它的父类包含更多的信息和方法。

2、父类中的私有数据域在该类之外不可访问，同样在子类中也不能直接使用，需要使用父类中的访问器/修改器来进行访问和修改。

3、在Java中，不允许多重继承，一个Java类只能直接继承自一个父类，这种限制称为单一继承。多重继承可以通过接口来实现。

 

posted @ 2016-07-25 20:27  xingzhui  阅读(1430)  评论(0)  编辑  收藏  举报