String replaceAll（）与Matcher replaceAll（）（性能差异） [英] String replaceAll() vs. Matcher replaceAll() (Performance differences)

问题描述

非常简单的问题，但这是来自一个C / C ++人进入Java的复杂性。

Pretty simple question, but this is coming from a C/C++ person getting into the intricacies of Java.

我知道我可以启动jUnit和一些性能我自己的测试得到答案;但我只是想知道它是否在那里。

I understand I can fire up jUnit and a few performance tests of my own to get an answer; but I'm just wondering if this is out there.

String.replaceAll（）和Matcher.replaceAll（）之间是否存在已知的差异（在匹配器上）在性能方面从Regex.Pattern创建的对象？

Are there known difference(s) between String.replaceAll() and Matcher.replaceAll() (On a Matcher Object created from a Regex.Pattern) in terms of performance?

此外，两者之间的高级API是什么区别？ （不变性，处理NULL，处理空字符串，制作咖啡等。）

Also, what are the high-level API 'ish differences between the both? (Immutability, Handling NULLs, Handling empty strings, making coffee etc.)

推荐答案

根据 String.replaceAll ，它有关于调用方法的以下内容：

According to the documentation for String.replaceAll, it has the following to say about calling the method:

形式的这种方法的调用 str.replaceAll（regex，repl）
产生与
完全相同的结果表达式

An invocation of this method of the form str.replaceAll(regex, repl) yields exactly the same result as the expression

Pattern.compile(regex).matcher(str).replaceAll(repl)

因此，可以预期调用 String.replaceAll之间的性能，并明确创建 Matcher 和 模式 应该是相同的。

Therefore, it can be expected the performance between invoking the String.replaceAll, and explicitly creating a Matcher and Pattern should be the same.

编辑

正如评论中指出的那样，性能差异不存在将是真实的从字符串或匹配单次调用 replaceAll ，但是，如果需要对 replaceAll 执行多次调用，可以预期保持已编译的模式，因此不必每次都执行相对昂贵的正则表达式模式编译。

As has been pointed out in the comments, the performance difference being non-existent would be true for a single call to replaceAll from String or Matcher, however, if one needs to perform multiple calls to replaceAll, one would expect it to be beneficial to hold onto a compiled Pattern, so the relatively expensive regular expression pattern compilation does not have to be performed every time.

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