要用双反斜杠替换单个反斜杠需要八个反斜杠? [英] Eight backslashes required to replace single backslash with double backslashes?

问题描述

这是一个到底发生了什么"的问题.我实际上不需要解决方案.

This is a "what the heck is going on here" question. I don't actually need a solution.

我必须用双反斜杠替换字符串中的所有单反斜杠.这就是我最终要做的...

I had to replace all single backslashes in a String with double backslashes . This is what I ended up doing...

strRootDirectory = strRootDirectory.replaceAll("\\\\", "\\\\\\\\");

...其中strRootDirectory是上面的java.lang.String.

...where strRootDirectory is a java.lang.String above.

现在，我理解第一个参数的四个反斜杠:regex期望两个反斜杠以表示单个文字反斜杠，而Java希望它们加倍.很好.

Now, I understand the four backslashes for the first argument: regex expects two backslashes in order to indicate a single literal backslash, and java wants them doubled up. That's fine.

但是，第二个参数的八个反斜杠到底是怎么回事?替换字符串不应该是文字字符串(我是说非正则表达式)吗?我希望在第二个参数中需要四个反斜杠，以便表示两个反斜杠.

BUT, what the heck is going on with the eight backslashes for the second argument? Isn't the replacement string supposed to be a literal (non-regex, I mean) string? I expected to need four backslashes in the second argument, in order to represent two backslashes.

推荐答案

第二个参数不是regex-string，而是regex-replacement-string，其中反斜杠也具有特殊含义(用于转义用于变量插值的特殊字符 $ ，也用于转义自身).

The second argument isn't a regex-string, but a regex-replacement-string, in which the backslash also has a special meaning (it is used to escape the special character $ used for variable interpolation and is also used to escape itself).

通过API:

请注意，替换字符串中的反斜杠( \ )和美元符号( $ )可能导致结果与被视为文字替换时的结果有所不同细绳;请参阅 Matcher.replaceAll .如果需要，可以使用 Matcher.quoteReplacement(java.lang.String)取消显示这些字符的特殊含义.

Note that backslashes (\) and dollar signs ($) in the replacement string may cause the results to be different than if it were being treated as a literal replacement string; see Matcher.replaceAll. Use Matcher.quoteReplacement(java.lang.String) to suppress the special meaning of these characters, if desired.

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