String.replaceAll single backslashes with double backslashes
backslash, escaping, java, replaceall
Solution
The `String#replaceAll()` interprets the argument as a regular expression. The `\` is an escape character in both `String` and `regex`. You need to double-escape it for regex:
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:
string.replace("\\", "\\\\");
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.
Problem
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: ``` theString.replaceAll("\\", "\\\\"); ``` But this gives the below exception: ``` java.util.regex.PatternSyntaxException: Unexpected internal error near index 1 ```