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Regex question

Ronald Schild
Ranch Hand

Joined: Jun 09, 2008
Posts: 117
Howdy,

I'm trying to replace "\\r" into "\r". What I've come up with is someString.replaceAll("\\\\r", "\r"), but this replaces "\r" with "r", and "\\r" with "\r".

Can anyone explain to me why it is doing this?


Java hobbyist.
Ronald Schild
Ranch Hand

Joined: Jun 09, 2008
Posts: 117
Aha.

Every regex '\' must be doubled, but also every string '\'. It does not replace "\\r" with "\r", it replaces "\r" with "r", a bit of confusion on my side.

More '\' is the way to go.

edit, so: "\\\\\\\\r" matches "\\r" (as parsed result).
[ July 16, 2008: Message edited by: Ronald Schild ]
Piet Verdriet
Ranch Hand

Joined: Feb 25, 2006
Posts: 266
In your case, there is no real need to use regex (as far as I can see). A simple String.replace(...) will do the job as well, and that method does not take a regex as parameter.
But, if you do need regex, and you want to keep the escaping to a minimum, you can always use \\Q ... \\E to make the regex engine ignore any meta characters:
<blockquote>code:
<pre name="code" class="core">String s = "Some text \\\\r and some more \\\\r.";
System.out.println(s);
System.out.println(s.replace("\\\\r", "\\r"));
System.out.println(s.replaceAll("\\Q\\\\r\\E", "\\\\r"));
</pre>
</blockquote>
 
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subject: Regex question