如何在Java中定义常量(Constant)

原本引自  http://blog.csdn.net/autofei/article/details/6419460

 1 /**
 2  * Method One
 3  */
 4 interface ConstantInterface {
 5     String SUNDAY = "SUNDAY";
 6     String MONDAY = "MONDAY";
 7     String TUESDAY = "TUESDAY";
 8     String WEDNESDAY = "WEDNESDAY";
 9     String THURSDAY = "THURSDAY";
10     String FRIDAY = "FRIDAY";
11     String SATURDAY = "SATURDAY";
12 }
13 /**
14  * Method Two 
15  */
16 enum ConstantEnum {
17     SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
18 }
19 /**
20  * Method Three
21  */
22 class ConstantClassField {
23     public static final String SUNDAY = "SUNDAY";
24     public static final String MONDAY = "MONDAY";
25     public static final String TUESDAY = "TUESDAY";
26     public static final String WEDNESDAY = "WEDNESDAY";
27     public static final String THURSDAY = "THURSDAY";
28     public static final String FRIDAY = "FRIDAY";
29     public static final String SATURDAY = "SATURDAY";
30 }
31 /**
32  * Method Four
33  * http://www.ibm.com/developerworks/cn/<a href="http://lib.csdn.net/base/17" class='replace_word' title="Java EE知识库" target='_blank' style='color:#df3434; font-weight:bold;'>Java</a>/l-java-interface/index.html
34  */
35 class ConstantClassFunction {
36     private static final String SUNDAY = "SUNDAY";
37     private static final String MONDAY = "MONDAY";
38     private static final String TUESDAY = "TUESDAY";
39     private static final String WEDNESDAY = "WEDNESDAY";
40     private static final String THURSDAY = "THURSDAY";
41     private static final String FRIDAY = "FRIDAY";
42     private static final String SATURDAY = "SATURDAY";
43     public static String getSunday() {
44         return SUNDAY;
45     }
46     public static String getMonday() {
47         return MONDAY;
48     }
49     public static String getTuesday() {
50         return TUESDAY;
51     }
52     public static String getWednesday() {
53         return WEDNESDAY;
54     }
55     public static String getThursday() {
56         return THURSDAY;
57     }
58     public static String getFirday() {
59         return FRIDAY;
60     }
61     public static String getSaturday() {
62         return SATURDAY;
63     }
64 }
65 public class TestConstant {
66     static final String day = "saturday";
67     public static void main(String[] args) {
68         System.out.println("Is today Saturday?");
69         System.out.println(day.equalsIgnoreCase(ConstantInterface.SATURDAY));
70         System.out.println(day.equalsIgnoreCase(ConstantEnum.SATURDAY.name()));
71         System.out.println(day.equalsIgnoreCase(ConstantClassField.SATURDAY));
72         System.out.println(day.equalsIgnoreCase(ConstantClassFunction
73                 .getSaturday()));
74     }
75 }

 

方法一采用接口(Interface)的中变量默认为static final的特性

方法二采用了Java 5.0中引入的Enum类型。

方法三采用了在普通类中使用static final修饰变量的方法。

方法四类似方法三，但是通过函数来获取常量。

 

首先定义全局变量似乎有违Java的面向对象的封装特性，增加的耦合。所以最佳的方法是避免定义全局变量。如果是参数等，可以写入配置文件。如果实在是必须的，方法二是最为推荐的。方法三是大家都能想到的，非常的直观。方法一和方法三本质上一样。方法四提供了灵活性，具体参考引用【1】。

参考

http://www.ibm.com/developerworks/cn/java/l-java-interface/index.html

 

posted @ 2016-04-20 16:23  SummerChill  阅读(12507)  评论(0)  编辑  收藏  举报