Removing literal character in regex

Question

I have the following string

\Qpipe,name=office1\E

And I am using a simplified regex library that doesn't support the \Q and \E.

I tried removing them

 s.replaceAll("\\Q", "").replaceAll("\\E", "")

However, I get the error Caused by: java.util.regex.PatternSyntaxException: Illegal/unsupported escape sequence near index 1 \E ^

Any ideas?

Answer 1

\ is the special escape character in both Java string and regex engine. To pass a literal \ to the regex engine you need to have \\\\ in the Java string. So try:

s.replaceAll("\\\\Q", "").replaceAll("\\\\E", "")

Alternatively and a simpler way would be to use the replace method which takes string and not regex:

s.replace("\\Q", "").replace("\\E", "")

Answer 2

Use the Pattern.quote() function to escape special characters in regex for example

s.replaceAll(Pattern.quote("\Q"), "")

Answer 3

replaceAll takes a regular expression string. Instead, just use replace which takes a literal string. So myRegexString.replace("\\Q", "").replace("\\E", "").

But that still leaves you with the problem of quoting special regex characters for your simplified regex library.