用Java声明项目常量的正确方法是什么？ [英] What's the proper way of declaring project constants in Java?
问题描述
对于Java开发人员来说，这似乎是一个愚蠢的问题，但是，我是Java的新手，我的背景是c级以下的知识。
我曾经包括一个头文件，其中包含与我的项目相关的所有常量。 （通常是#define）。
我现在正在从事一个大型Java项目，我需要使一些常量成为全局常量（它们适合多个类，并在项目的各个部分中使用）
This may seems a silly question for Java developers, however, I'm new to Java, and my background is from low level c. I used to include an header file with all the constants that were relevant for my projects. (usually #define's). I'm working on a big Java project now, and there a few constants I need to make global (they fit in more than one class, and used in various parts of the project )
这让我很难决定将其放置在哪里，我是否应该多次声明相同的常量，每个类一次？
It makes it hard for me to decide where to put it, should I declare the same constant few times, one in each class ?
很多框架都使用XML文件声明常量&框架的定义（Hibernate，Log4J等）在我的项目中使用这种技术是否明智？如果是这样，如何轻松完成？
A lot of framework, uses XML files to declare constants & definitions for the framework (Hibernate, Log4J, etc.) Is it wise to use this kind of technique in my project ? if so, how can it be done easily ?
推荐答案
与很多事情一样，有很多方法可以做到这一点。您不应该做的一件事是多次声明它们-这简直是愚蠢的。 ：P
As with many things, there are many ways to do it. One thing you should not do is declare them multiple times - that's just plain silly. :P
一切都必须放在Java类中，所以要么：
Everything has to be in a class in Java, so either:
- 选择一个主类（例如，我有一个名为 FTPServerApp的项目-我可以将它们放在那里）
- 创建一个包含所有它们的 Util类
弄清楚放置它们的位置时，请完全声明它们：
When you figure out where to put them, declare them all this way:
public static final [type] [NAME_IN_ALL_CAPS] = [value];
这将
- 使它们可用于任何地方的所有项目代码（
公共） - 在所有实例中仅存在值的一个副本类（
static） - 它们不能更改（
final）
- make them available to all your project code, anywhere (
public) - only one copy of the value exists across all instances of the class (
static) - they cannot be changed (
final).
ALL_CAPS_FOR_CONSTANT_NAMES 是Java中的约定。
The ALL_CAPS_FOR_CONSTANT_NAMES, separated by underscores, is the convention in Java.
因此，如果在名为 FTPServerAPP 的类中声明了该变量，则您有一个名为<$ c $的常量。 c> SERVICE_PORT 可能是：
So, if this was declared in a class called FTPServerAPP, and you had a constant called SERVICE_PORT it might be:
public class FTPServerApp {
public static final int SERVICE_PORT = 21;
...
}
...可以从任何类访问它，就像这样...
...and you would access it, from any class, like this...
FTPServerApp.SERVICE_PORT
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