那么枚举呢?

I use static final to declare constants and go with the ALL_CAPS naming notation. I have seen quite a few real life instances where all constants are bunched together into an interface. A few posts have rightly called that a bad practice, primarily because that's not what an interface is for. An interface should enforce a contract and should not be a place to put unrelated constants in. Putting it together into a class that cannot be instantiated (through a private constructor) too is fine if the constant semantics don't belong to a specific class(es). I always put a constant in the class that it's most related to, because that makes sense and is also easily maintainable.

枚举是表示一组值的好选择，但是如果您要存储强调绝对值的独立常量(例如。TIMEOUT = 100 ms)你可以直接使用静态的final方法。

在单独的类中创建静态final常量可能会给您带来麻烦。Java编译器实际上会对此进行优化，并将常量的实际值放置到引用它的任何类中。

如果你稍后更改了Constants类，并且没有对引用该类的其他类进行严格的重新编译，那么你最终将使用新旧值的组合。

不要把它们看作常量，而应该把它们看作配置参数，并创建一个类来管理它们。让值是非final的，甚至可以考虑使用getter。将来，当您确定其中一些参数实际上应该由用户或管理员进行配置时，这将变得容易得多。

对于常量，Enum是一个更好的选择。这里有一个例子

公共类myClass {

public enum myEnum {
    Option1("String1", 2), 
    Option2("String2", 2) 
    ;
    String str;
            int i;

            myEnum(String str1, int i1) { this.str = str1 ; this.i1 = i }


}

我强烈建议不要只使用一个常量类。这在当时看起来是一个好主意，但是当开发人员拒绝记录常量，并且类增长到包含500个以上彼此完全不相关的常量(与应用程序的完全不同方面相关)时，通常会导致常量文件完全不可读。而不是:

If you have access to Java 5+, use enums to define your specific constants for an application area. All parts of the application area should refer to enums, not constant values, for these constants. You may declare an enum similar to how you declare a class. Enums are perhaps the most (and, arguably, only) useful feature of Java 5+. If you have constants that are only valid to a particular class or one of its subclasses, declare them as either protected or public and place them on the top class in the hierarchy. This way, the subclasses can access these constant values (and if other classes access them via public, the constants aren't only valid to a particular class...which means that the external classes using this constant may be too tightly coupled to the class containing the constant) If you have an interface with behavior defined, but returned values or argument values should be particular, it is perfectly acceptible to define constants on that interface so that other implementors will have access to them. However, avoid creating an interface just to hold constants: it can become just as bad as a class created just to hold constants.

在Effective Java(第二版)中，建议对常量使用枚举而不是静态整型。

这里有一篇很好的关于Java中枚举的文章: http://java.sun.com/j2se/1.5.0/docs/guide/language/enums.html

请注意，在那篇文章的最后提出的问题是:

那么什么时候应该使用枚举呢?

答案为:

任何时候你需要一个固定的常数集