更进一步，您可以将全局使用的常量放在接口中，这样它们就可以在系统范围内使用。如。

public interface MyGlobalConstants {
    public static final int TIMEOUT_IN_SECS = 25;
}

但是不要执行它。只需在代码中通过完全限定类名直接引用它们。

那么枚举呢?

您可能犯的第一个错误是创建一个全局可访问的类，类名为泛型名称，如Constants。这只会充斥着垃圾，您将无法确定系统的哪个部分使用了这些常量。

相反，常量应该放到“拥有”它们的类中。有一个叫TIMEOUT的常量吗?它应该放到Communications()或Connection()类中。MAX_BAD_LOGINS_PER_HOUR吗?进入User()。诸如此类。

当“常量”可以在运行时定义，但用户不容易更改时，另一种可能的用法是Java .properties文件。你可以把它们打包到你的.jar文件中，并使用Class resourceLoader引用它们。

有一定的观点来回答这个问题。首先，java中的常量通常被声明为public、static和final。原因如下:

public, so that they are accessible from everywhere
static, so that they can be accessed without any instance. Since they are constants it
  makes little sense to duplicate them for every object.
final, since they should not be allowed to change

我永远不会为CONSTANTS访问器/对象使用接口，因为接口通常是需要实现的。这看起来是不是很有趣:

String myConstant = IMyInterface.CONSTANTX;

相反，我会在一些不同的方法中进行选择，基于一些小的权衡，所以这取决于你需要什么:

1.  Use a regular enum with a default/private constructor. Most people would define 
     constants this way, IMHO.
  - drawback: cannot effectively Javadoc each constant member
  - advantage: var members are implicitly public, static, and final
  - advantage: type-safe
  - provides "a limited constructor" in a special way that only takes args which match
     predefined 'public static final' keys, thus limiting what you can pass to the
     constructor

2.  Use a altered enum WITHOUT a constructor, having all variables defined with 
     prefixed 'public static final' .
  - looks funny just having a floating semi-colon in the code
  - advantage: you can JavaDoc each variable with an explanation
  - drawback: you still have to put explicit 'public static final' before each variable
  - drawback: not type-safe
  - no 'limited constructor'

3.  Use a Class with a private constructor:
  - advantage: you can JavaDoc each variable with an explanation
  - drawback: you have to put explicit 'public static final' before each variable
  - you have the option of having a constructor to create an instance
     of the class if you want to provide additional functions related
     to your constants 
     (or just keep the constructor private)
  - drawback: not type-safe

4. Using interface:
  - advantage: you can JavaDoc each variable with an explanation
  - advantage: var members are implicitly 'public static final'
  - you are able to define default interface methods if you want to provide additional
     functions related to your constants (only if you implement the interface)
  - drawback: not type-safe

静态final是我的偏好，我只使用enum如果项目确实是可枚举的。

更进一步，您可以将全局使用的常量放在接口中，这样它们就可以在系统范围内使用。如。

public interface MyGlobalConstants {
    public static final int TIMEOUT_IN_SECS = 25;
}

但是不要执行它。只需在代码中通过完全限定类名直接引用它们。