Java中if / else与switch语句的相对性能差异是什么？ [英] What is the relative performance difference of if/else versus switch statement in Java?
问题描述
担心我的网络应用程序的性能，我想知道哪个if / else或switch语句在性能方面更好？
Worrying about my web application's performances, I am wondering which of "if/else" or switch statement is better regarding performance?
推荐答案
这是微观优化和过早优化，这是邪恶的。而是担心有问题的代码的可读性和可维护性。如果有两个以上 if / else 块粘在一起或其大小不可预测，那么你可能会高度考虑一个开关声明。
That's micro optimization and premature optimization, which are evil. Rather worry about readabililty and maintainability of the code in question. If there are more than two if/else blocks glued together or its size is unpredictable, then you may highly consider a switch statement.
或者，您也可以抓取多态性。首先创建一些接口：
Alternatively, you can also grab Polymorphism. First create some interface:
public interface Action {
void execute(String input);
}
并获取某些 Map <中的所有实现/ code>。您可以静态或动态地执行此操作：
And get hold of all implementations in some Map. You can do this either statically or dynamically:
Map<String, Action> actions = new HashMap<String, Action>();
最后替换 if / else 或切换这样的事情（留下无效的支票，如无效指针）：
Finally replace the if/else or switch by something like this (leaving trivial checks like nullpointers aside):
actions.get(name).execute(input);
可能比更小于if / else 或切换，但代码至少可以更好地维护。
It might be microslower than if/else or switch, but the code is at least far better maintainable.
当您谈论网络应用时，您可以使用 HttpServletRequest＃getPathInfo（） 作为操作键（最终写一些代码，在循环中将pathinfo的最后一部分分开，直到找到一个动作）。你可以在这里找到类似的答案：
As you're talking about webapplications, you can make use of HttpServletRequest#getPathInfo() as action key (eventually write some more code to split the last part of pathinfo away in a loop until an action is found). You can find here similar answers:
- Using a custom Servlet oriented framework, too many servlets, is this an issue
- Java Front Controller
如果您一般担心Java EE Web应用程序的性能，那么您可能会发现这篇文章也很有用。除了（微）优化原始Java代码之外，还有其他领域提供更多性能增益。
If you're worrying about Java EE webapplication performance in general, then you may find this article useful as well. There are other areas which gives a much more performance gain than only (micro)optimizing the raw Java code.
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