Groovy：为什么我需要加倍转义方括号？ [英] Groovy: Why do I need to double escape square brackets?

问题描述

为什么这不起作用？

"hello[world".split("\[")

并且这样做：

and this does:

"hello[world".split("\\[")

推荐答案

这实际上是两个在不同上下文中的转义，因为参数是一个表示为字符串的正则表达式。

This is actually two escapes in different contexts, due to the fact that the argument is a regular expression represented as a string.

[必须被转义，否则它在正则表达式中会有特殊含义。正则表达式的转义会使它 \ [。但是， \ 必须被转义，因为它在字符串中有特殊含义（用于转义和用数字值表示字符）。

The [ has to be escaped because otherwise it would have a special meaning in the regular expression. The escape for the regular expression would make it \[. But then the \ has to be escaped as it has special meaning in a string (for escaping and for representing characters by numeric value).

可能会更糟糕，因为 \ 字符用于在上下文中转义。如果要按 \ 字符进行拆分，则必须将其转义（ \\ ）正则表达式的用法，但是你有两个 \ 字符，这两个字符必须在字符串上下文中转义。如果你把它写成一个常量，那么在你正在分割的原始字符串中的用法也需要转义，所以类似的分割将如下所示：

It can be much worse, as the \ character is used for escaping in both contexts. If you want to split by the \ character, you have to escape it (\\) for the regular expression usage, but then you have two \ characters, which both have to be escaped in string context. The usage in the original string you are splitting would also need the escape if you're writing it as a constant, so the analogous split would look like:

"hello\\world".split("\\\\")

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