Java doesn't work with regex \s, says: invalid escape sequence

Question

I want to replace all whitespace characters in a string with a "+" and all "ß" with "ss"... it works well for "ß", but somehow eclipse won't let me use \s for a whitespace.. I tried "\t" instead, but it doesn't work either.. I get the following error:

Invalid escape sequence (valid ones are \b \t \n \f \r \" \' \ )

this is my code:

try {
    String temp1 = from.getText().toString();
    start_from  = temp1.replaceAll("ß", "ss");
    start_from  = start_from.replaceAll("\s", "+");
}

why doesn't it work? is it a problem with android, eclipse or what?

thanks in advance!

I'm surprised that you can even compile \s in a string literal. Adding \t in a string literal would create a regular expression containing a tab character, rather than the regular expression with \t in it, for that you need \\t in the string literal. — Geoff
– Geoff, Commented Apr 28, 2010 at 21:35
I couldn't compile it,.. eclipse gave me this error message I posted. I just wanted to let you know what I was trying to do. — MJVDM
– MJVDM, Commented Apr 28, 2010 at 22:20

Pshemo · Accepted Answer · 2014-07-31 20:02:44Z

74

You need to escape the slash

start_from  = start_from.replaceAll("\\s", "+");

edited Jul 31, 2014 at 20:02

Pshemo

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answered Apr 28, 2010 at 21:27

Rob Di Marco

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1 Comment

MJVDM Over a year ago

thank you! awesome website! :-) "You cannot accept an answer in 11 minutes" .... ;-)

David Hedlund · Accepted Answer · 2010-04-28 21:30:03Z

12

The problem is that \ is an escape character in java as well as regex patterns. If you want to match the regex pattern \n, say, and you'd go ahead and write

replaceAll("\n", "+");

The regex pattern would not end up being \n: it would en up being an actual newline, since that's what "\n" means in Java. If you want the pattern to contain a backslash, you'll need to make sure you escape that backslash, so that it is not treated as a special character within the string.

replaceAll("\\s", "+");

answered Apr 28, 2010 at 21:30

David Hedlund

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Comments

Dustin · Accepted Answer · 2010-04-28 21:34:23Z

1

You can use the java.util.regex.Pattern class and use something like p = Pattern.compile("\s"); in combination with p.matcher(start_from).replaceAll("+"). Alternatively, just escape your "\s" metacharacter as "\\s".

answered Apr 28, 2010 at 21:34

Dustin

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1 Comment

MJVDM Over a year ago

jepp I already used a pattern in another part of my code, however, I thought it would be easier in this case to just use replaceAll(..) thank you!

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