如何使用Java包？ [英] How to use Java packages?

问题描述

为什么我们在Java中使用包？
如何使用它们？

Why do we use packages in Java? How to use them?

推荐答案

软件包主要是只是组织代码的一种方式。 JDK有数千个类，大型应用程序有数千个类。为什么不想要将这些组织成某种层次结构，以便您轻松找到您感兴趣的课程？

Packages are mostly just a way of organizing code. The JDK has thousands of classes in, and a large application has thousands more. Why would you not want to organize those into some sort of hierarchy allowing you to find the classes you're interested in easily?

包还参与Java中的访问控制（但不是在.NET中，有趣的是） - 但我要说的主要目的是帮助人有意义地组织他们的代码。

Packages also participate in access control in Java (but not in .NET, interestingly) - but I'd say the main purpose is to help humans organize their code meaningfully.

它也意味着您可能偶尔需要或需要多个包中的相同类名 - 其中包名有效地提供了上下文。现在，如果你在单个代码库中为单个应用程序工作，那么通常要试图避免 - 但如果你有一个大型代码库，许多不同的应用程序使用它的许多不同部分，这可能比尝试为每个类都有一个唯一的名称更好。 （一个典型的例子是用户界面代码 - 只是查看.NET库，在三个独立的UI框架中有三个独立的命名空间中的Button类。）

It also means that occasionally you may want or need the same class name in multiple packages - where the package name effectively provides the context. Now if you're working in a single codebase for a single application, that's usually something to try to avoid - but if you've got a large codebase where many different applications use many different parts of it, that may be better than trying to have a unique name for every single class. (A typical example of this is in user interface code - just looking in the .NET libraries, there's a "Button" class in three separate namespaces, for three separate UI frameworks.)

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