普通类实现枚举与抽象类的应用比较

普通类实现枚举与抽象类的应用比较

分类： Java 2012-06-05 12:00 560人阅读 评论(0)收藏举报

stringclass测试

当我们想实现一个星期几的枚举时候我们自己编写一个类来实现！如果我们用实体类的代码如下：

[java] view plaincopyprint?

1. package com.jemsn.weekday;
3. public class WeekDay {
4. //构造函数私有化 让别人不可以再创建新的对象实例
5. private WeekDay () {}
6. public static final WeekDay MonDay=new WeekDay();
7. public staticfinal WeekDay Tuesay=new WeekDay();
8. public static final WeekDay WendsDay=new WeekDay();
9. public staticfinal WeekDay ThusDay=new WeekDay();
10. public static final WeekDay FriDay=new WeekDay();
11. public staticfinal WeekDay StaDay=new WeekDay();
12. public static final WeekDay SunDay=new WeekDay();
13. //如果我们要一个NextDay()方法
14. public WeekDay NextDay() {
15. if(this==MonDay){
16. return Tuesay;
17. }else if(this==Tuesay){
18. return WendsDay;
19. }
20. else if(this==WendsDay){
21. return ThusDay;
22. }
23. else if(this==ThusDay){
24. return FriDay;
25. }
26. else if(this==FriDay){
27. return StaDay;
28. }
29. else if(this==StaDay){
30. return SunDay;
31. }else {
32. return MonDay;
33. }
36. }
37. //重写ToString方法
38. public String toString() {
39. return this==MonDay?"星期一":this==Tuesay?"星期二":this==WendsDay?"星期三":this==ThusDay?"星期四":"星期五";
40. }
42. }

package com.jemsn.weekday;public class WeekDay {//构造函数私有化 让别人不可以再创建新的对象实例private WeekDay () {}   public static final WeekDay MonDay=new WeekDay();   public static final WeekDay Tuesay=new WeekDay();   public static final WeekDay WendsDay=new WeekDay();   public static final WeekDay ThusDay=new WeekDay();   public static final WeekDay FriDay=new WeekDay();   public static final WeekDay StaDay=new WeekDay();   public static final WeekDay SunDay=new WeekDay();   //如果我们要一个NextDay()方法   public WeekDay NextDay() {   if(this==MonDay){   return Tuesay;   }else if(this==Tuesay){   return WendsDay;   }      else if(this==WendsDay){   return ThusDay;   }   else if(this==ThusDay){   return FriDay;   }   else if(this==FriDay){   return StaDay;   }   else if(this==StaDay){   return SunDay;   }else {return MonDay;} } //重写ToString方法public String toString() { return this==MonDay?"星期一":this==Tuesay?"星期二":this==WendsDay?"星期三":this==ThusDay?"星期四":"星期五";}   }

然后我们在测试代码里调用它：

[java] view plaincopyprint?

1. package com.jemsn.weekday;
3. public class test {
5. public staticvoid main(String[] args) {
6. WeekDay monday=WeekDay.MonDay;
7. WeekDay tuesday=WeekDay.Tuesay;
8. System.out.println(monday.NextDay());
9. System.out.println(tuesday.NextDay());
10. }
12. }

package com.jemsn.weekday;public class test {  public static void main(String[] args) {WeekDay monday=WeekDay.MonDay;WeekDay tuesday=WeekDay.Tuesay;System.out.println(monday.NextDay());System.out.println(tuesday.NextDay());}}

输出结果如下：

-----------------------------------------------------------------------

星期二
星期三

-----------------------------------------------------------------------

上面的代码我们可以看出，在我们的NextDay方法中用了一大堆的if else else if 之类的，如果我们装基改为抽象类，如下代码：

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1. package com.jemsn.weekday;
3. public abstractclass WeekDay {
4. //构造函数私有化 让别人不可以再创建新的对象实例
5. private WeekDay () {}
6. public static final WeekDay MonDay=new WeekDay(){
8. public WeekDay NextDay() {
9. return WeekDay.Tuesay;
10. }
12. };
13. //采用了匿名内部类的实现方式
14. public static final WeekDay Tuesay=new WeekDay(){
16. public WeekDay NextDay() {
17. return WeekDay.WendsDay;
18. }
20. };
21. public staticfinal WeekDay WendsDay=new WeekDay(){
23. public WeekDay NextDay() {
24. return WeekDay.ThusDay;
25. }
27. };
28. public static final WeekDay ThusDay=new WeekDay(){
30. public WeekDay NextDay() {
31. return WeekDay.FriDay;
32. }
34. };
35. public staticfinal WeekDay FriDay=new WeekDay(){
37. public WeekDay NextDay() {
38. return WeekDay.StaDay;
39. }
41. };
42. public static final WeekDay StaDay=new WeekDay(){
44. public WeekDay NextDay() {
45. return WeekDay.SunDay;
46. }
48. };
49. public staticfinal WeekDay SunDay=new WeekDay(){
51. public WeekDay NextDay() {
52. return WeekDay.MonDay;
53. }
55. };
56. //如果我们要一个NextDay()方法
57. public abstract WeekDay NextDay();
61. //重写ToString方法
62. public String toString() {
63. return this==MonDay?"星期一":this==Tuesay?"星期二":this==WendsDay?"星期三":this==ThusDay?"星期四":"星期五";
64. }
66. }

package com.jemsn.weekday;public abstract class WeekDay {//构造函数私有化 让别人不可以再创建新的对象实例private WeekDay () {}   public static final WeekDay MonDay=new WeekDay(){ public WeekDay NextDay() {return WeekDay.Tuesay;}      };   //采用了匿名内部类的实现方式   public static final WeekDay Tuesay=new WeekDay(){   public WeekDay NextDay() {return WeekDay.WendsDay;}      };   public static final WeekDay WendsDay=new WeekDay(){   public WeekDay NextDay() {return WeekDay.ThusDay;}      };   public static final WeekDay ThusDay=new WeekDay(){   public WeekDay NextDay() {return WeekDay.FriDay;}      };   public static final WeekDay FriDay=new WeekDay(){   public WeekDay NextDay() {return WeekDay.StaDay;}      };   public static final WeekDay StaDay=new WeekDay(){   public WeekDay NextDay() {return WeekDay.SunDay;}      };   public static final WeekDay SunDay=new WeekDay(){   public WeekDay NextDay() {return WeekDay.MonDay;}      };   //如果我们要一个NextDay()方法   public abstract WeekDay NextDay();   //重写ToString方法public String toString() { return this==MonDay?"星期一":this==Tuesay?"星期二":this==WendsDay?"星期三":this==ThusDay?"星期四":"星期五";}   }

上面的代码中我们将if else分别转化成了一个个独立的类，测试代码不变，输出的结果如下 ：

-----------------------------------------------------------------------

星期二
星期三

-----------------------------------------------------------------------

我们看到的还是一样，但是实现的方式却完全不一样！所以我们可以总结用抽象方法结合匿名内部类实现比统一的更加好！