原本引自
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, SATURDAY18 }19 /**20 * Method Three21 */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 Four33 * http://www.ibm.com/developerworks/cn/Java/l-java-interface/index.html34 */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(ConstantClassFunction73 .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