为什么使用带有Java import语句的外卡不好？ [英] Why is using a wild card with a Java import statement bad?

问题描述

使用单个语句更方便，更清晰

It is much more convenient and cleaner to use a single statement like

import java.awt.*;

而不是导入一堆个别课程

than to import a bunch of individual classes

import java.awt.Panel;
import java.awt.Graphics;
import java.awt.Canvas;
...

在 import 声明？

推荐答案

唯一的问题是它会使你的本地命名空间变得混乱。例如，假设您正在编写Swing应用程序，因此需要 java.awt.Event ，并且还要与公司的日历系统连接，该系统具有 com.mycompany.calendar.Event 。如果使用通配符方法导入两者，则会发生以下三种情况之一：

The only problem with it is that it clutters your local namespace. For example, let's say that you're writing a Swing app, and so need java.awt.Event, and are also interfacing with the company's calendaring system, which has com.mycompany.calendar.Event. If you import both using the wildcard method, one of these three things happens:

1. java.awt.Event 和 com.mycompany.calendar.Event ，所以你甚至无法编译。


2. 你实际上只管理导入一个（两个导入中只有一个导入。* ），但这是错误的，你很难弄清楚为什么你的代码声称类型错误。


3. 编译代码时没有 com.mycompany.calendar.Event ，但是当他们以后添加一个你以前有效的代码突然停止编译。

1. You have an outright naming conflict between java.awt.Event and com.mycompany.calendar.Event, and so you can't even compile.
2. You actually manage only to import one (only one of your two imports does .*), but it's the wrong one, and you struggle to figure out why your code is claiming the type is wrong.
3. When you compile your code there is no com.mycompany.calendar.Event, but when they later add one your previously valid code suddenly stops compiling.

明确列出所有进口的优势是我可以告诉你看一下你打算使用哪个类，这简单地使得阅读代码变得更加容易。如果你只是做一个快速的一次性事情，没有明确的错误，但未来的维护者会感谢你的清晰度。

The advantage of explicitly listing all imports is that I can tell at a glance which class you meant to use, which simply makes reading the code that much easier. If you're just doing a quick one-off thing, there's nothing explicitly wrong, but future maintainers will thank you for your clarity otherwise.

这篇关于为什么使用带有Java import语句的外卡不好？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！