Java String.replaceAll 带有双反斜杠的单反斜杠

String.replaceAll single backslashes with double backslashes

提问by Frank Groeneveld

I'm trying to convert the String\something\into the String\\something\\using replaceAll, but I keep getting all kinds of errors. I thought this was the solution:

我正在尝试将 theString\something\转换为String\\something\\using replaceAll，但我不断收到各种错误。我认为这是解决方案：

theString.replaceAll("\", "\\");

But this gives the below exception:

但这给出了以下例外：

java.util.regex.PatternSyntaxException: Unexpected internal error near index 1

采纳答案by BalusC

The String#replaceAll()interprets the argument as a regular expression. The \is an escape character in bothStringand regex. You need to double-escape it for regex:

将String#replaceAll()参数解释为正则表达式。该\是转义字符都String和regex。您需要为正则表达式双重转义它：

string.replaceAll("\\", "\\\\");

But you don't necessarily need regex for this, simply because you want an exact character-by-character replacement and you don't need patterns here. So String#replace()should suffice:

但是您不一定需要为此使用正则表达式，仅仅因为您想要一个逐个字符的精确替换，而您不需要这里的模式。所以String#replace()应该足够了：

string.replace("\", "\\");

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Update: as per the comments, you appear to want to use the string in JavaScript context. You'd perhaps better use StringEscapeUtils#escapeEcmaScript()instead to cover more characters.

更新：根据评论，您似乎想在 JavaScript 上下文中使用该字符串。你也许最好用它StringEscapeUtils#escapeEcmaScript()来覆盖更多的字符。

回答by sfussenegger

You'll need to escape the (escaped) backslash in the first argument as it is a regular expression. Replacement (2nd argument - see Matcher#replaceAll(String)) also has it's special meaning of backslashes, so you'll have to replace those to:

您需要在第一个参数中转义（转义）反斜杠，因为它是一个正则表达式。替换（第二个参数 - 请参阅Matcher#replaceAll(String)）也具有反斜杠的特殊含义，因此您必须将它们替换为：

theString.replaceAll("\\", "\\\\");

回答by Jonathan Feinberg

Yes... by the time the regex compiler sees the pattern you've given it, it sees only a single backslash (since Java's lexer has turned the double backwhack into a single one). You need to replace "\\\\"with "\\\\", believe it or not! Java really needs a good raw string syntax.

是的...当正则表达式编译器看到您提供的模式时，它只会看到一个反斜杠（因为 Java 的词法分析器已将双反斜杠变成了一个反斜杠）。您需要更换"\\\\"有"\\\\"，信不信由你！Java 确实需要一个好的原始字符串语法。

回答by Fabian Steeg

To avoid this sort of trouble, you can use replace(which takes a plain string) instead of replaceAll(which takes a regular expression). You will still need to escape backslashes, but not in the wild ways required with regular expressions.

为了避免这种麻烦，您可以使用replace(它需要一个普通字符串) 而不是replaceAll(它需要一个正则表达式)。您仍然需要转义反斜杠，但不需要以正则表达式所需的疯狂方式。

回答by Pshemo

TLDR: use theString = theString.replace("\\", "\\\\");instead.

TLDR：theString = theString.replace("\\", "\\\\");改为使用。

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Problem

问题

replaceAll(target, replacement)uses regular expression (regex) syntax for targetand partially for replacement.

replaceAll(target, replacement)使用正则表达式 (regex) 语法用于target和部分用于replacement.

Problem is that \is special character in regex (it can be used like \dto represents digit) and in String literal (it can be used like "\n"to represent line separator or \"to escape double quote symbol which normally would represent end of string literal).

问题是它\是正则表达式中的特殊字符（它可以用来\d表示数字）和字符串文字（它可以用来"\n"表示行分隔符或\"转义通常表示字符串文字结尾的双引号）。

In both these cases to create \symbol we can escapeit (make it literal instead of special character) by placing additional \before it (like we escape "in string literals via \").

在这两种创建\符号的情况下，我们可以通过在它之前放置额外的（就像我们在字符串文字中通过转义）来转义它（使其成为文字而不是特殊字符）。\"\"

So to targetregex representing \symbol will need to hold \\, and string literal representing such text will need to look like "\\\\".

因此，target表示\符号的正则表达式需要保持\\，而表示此类文本的字符串文字需要看起来像"\\\\".

So we escaped \twice:

所以我们逃了\两次：

• once in regex \\
• once in String literal "\\\\"(each \is represented as "\\").

• 一次在正则表达式中 \\
• 一次在字符串文字中"\\\\"（每个\都表示为"\\"）。

In case of replacement\is also special there. It allows us to escape other special character $which via $xnotation, allows us to use portion of data matched by regex and held by capturing group indexed as x, like "012".replaceAll("(\\d)", "$1$1")will match each digit, place it in capturing group 1 and $1$1will replace it with its two copies (it will duplicate it) resulting in "001122".

万一replacement\也有特别之处。它允许我们$通过$x符号转义其他特殊字符，允许我们使用由正则表达式匹配并由捕获组索引为 的部分数据x，例如"012".replaceAll("(\\d)", "$1$1")将匹配每个数字，将其放置在捕获组 1 中并将$1$1其替换为其两个副本（它会复制它）导致"001122".

So again, to let replacementrepresent \literal we need to escape it with additional \which means that:

所以再次，为了让replacement代表\文字我们需要用额外的\方式来转义它，这意味着：

• replacement must hold two backslash characters \\
• and String literal which represents \\looks like "\\\\"

• 替换必须包含两个反斜杠字符 \\
• 和代表\\看起来像的字符串文字"\\\\"

BUT since we want replacementto hold twobackslashes we will need "\\\\\\\\"(each \represented by one "\\\\").

但是因为我们想要replacement保存两个反斜杠，所以我们需要"\\\\\\\\"（每个\用一个 表示"\\\\"）。

So version with replaceAllcan look like

所以版本replaceAll看起来像

replaceAll("\\", "\\\\");

Easier way

更简单的方法

To make out life easier Java provides tools to automatically escape text into targetand replacementparts. So now we can focus only on strings, and forget about regex syntax:

为了让生活更轻松，Java 提供了工具来自动将文本转义为target和replacement部分。所以现在我们可以只关注字符串，而忘记正则表达式语法：

replaceAll(Pattern.quote(target), Matcher.quoteReplacement(replacement))

which in our case can look like

在我们的例子中，它看起来像

replaceAll(Pattern.quote("\"), Matcher.quoteReplacement("\\"))

Even better

甚至更好

If we don't really need regex syntax support lets not involve replaceAllat all. Instead lets use replace. Both methods will replace alltargets, but replacedoesn't involve regex syntax. So you could simply write

如果我们真的不需要正则表达式语法支持，就不要参与replaceAll。相反，让我们使用replace. 两种方法都将替换所有targets，但replace不涉及正则表达式语法。所以你可以简单地写

theString = theString.replace("\", "\\");