首先看示例：

/**
*MethodOne
*/
interfaceConstantInterface{
StringSUNDAY="SUNDAY";
StringMONDAY="MONDAY";
StringTUESDAY="TUESDAY";
StringWEDNESDAY="WEDNESDAY";
StringTHURSDAY="THURSDAY";
StringFRIDAY="FRIDAY";
StringSATURDAY="SATURDAY";
}
/**
*MethodTwo
*/
enumConstantEnum{
SUNDAY,MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY
}
/**
*MethodThree
*/
classConstantClassField{
publicstaticfinalStringSUNDAY="SUNDAY";
publicstaticfinalStringMONDAY="MONDAY";
publicstaticfinalStringTUESDAY="TUESDAY";
publicstaticfinalStringWEDNESDAY="WEDNESDAY";
publicstaticfinalStringTHURSDAY="THURSDAY";
publicstaticfinalStringFRIDAY="FRIDAY";
publicstaticfinalStringSATURDAY="SATURDAY";
}
/**
*MethodFour
*http://www.ibm.com/developerworks/cn/java/l-java-interface/index.html
*/
classConstantClassFunction{
privatestaticfinalStringSUNDAY="SUNDAY";
privatestaticfinalStringMONDAY="MONDAY";
privatestaticfinalStringTUESDAY="TUESDAY";
privatestaticfinalStringWEDNESDAY="WEDNESDAY";
privatestaticfinalStringTHURSDAY="THURSDAY";
privatestaticfinalStringFRIDAY="FRIDAY";
privatestaticfinalStringSATURDAY="SATURDAY";
publicstaticStringgetSunday(){
returnSUNDAY;
}
publicstaticStringgetMonday(){
returnMONDAY;
}
publicstaticStringgetTuesday(){
returnTUESDAY;
}
publicstaticStringgetWednesday(){
returnWEDNESDAY;
}
publicstaticStringgetThursday(){
returnTHURSDAY;
}
publicstaticStringgetFirday(){
returnFRIDAY;
}
publicstaticStringgetSaturday(){
returnSATURDAY;
}
}
publicclassTestConstant{
staticfinalStringday="saturday";
publicstaticvoidmain(String[]args){
System.out.println("IstodaySaturday?");
System.out.println(day.equalsIgnoreCase(ConstantInterface.SATURDAY));
System.out.println(day.equalsIgnoreCase(ConstantEnum.SATURDAY.name()));
System.out.println(day.equalsIgnoreCase(ConstantClassField.SATURDAY));
System.out.println(day.equalsIgnoreCase(ConstantClassFunction
.getSaturday()));
}
}

方法一采用接口(Interface)的中變量默認為static final的特性。

方法二采用了Java 5.0中引入的Enum類型。

方法三采用了在普通類中使用static final修飾變量的方法。

方法四類似方法三，但是通過函數來獲取常量。

首先定義全局變量似乎有違Java的面向對象的封裝特性，增加的耦合。所以最佳的方法是避免定義全局變量。如果是參數等，可以寫入配置文件。如果實在是必須的，方法二是最為推薦的。方法三是大家都能想到的，非常的直觀。方法一和方法三本質上一樣。方法四提供了靈活性，具體參考引用【1】。

總結

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