Java regex pattern to match word or phrase

Question

I have the following regular expression, that I am compiling with Pattern class.

\bIntegrated\s+Health\s+System\s+\(IHS\)\b

Why is this not matching this string?

"test pattern case Integrated Health System (IHS)."

If I try \bpattern\b, it seems to work, but for the above phrase it does not. I have the parenthesis in the pattern escaped, so not sure why it doesn't work. It does match if I remove the parenthesis portion of the pattern, but I want to match the whole thing.

I did escape it, stackoverflow un-escaped :). My expression reads like this: <code>\bIntegrated\s+Health\s+System\s+$IHS$\b</code> — Eqbal
– Eqbal, Commented Jan 5, 2010 at 23:30
SO doesn't know <code> tags. Just indent with 4 spaces or select it and press 010101 button or Ctrl+K. Also see the Markdown FAQ on the right hand of the message editor. — BalusC
– BalusC, Commented Jan 5, 2010 at 23:33

Paul Creasey · Accepted Answer · 2010-01-05 23:48:47Z

1

1) escape the parens, otherwise they are capturing and group metacharacters, not literal parenthesis 

2) remove the final \b you can't use a word boundary after a literal ), since ) is not considered part of a word.

\bIntegrated\s+Health\s+System\s+\(IHS\)\W

edited Jan 5, 2010 at 23:48

answered Jan 5, 2010 at 23:26

Paul Creasey

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6 Comments

Eqbal Over a year ago

Okay, how do I indicate the trailing boundary then, so it does not match something like \bIntegrated\s+Health\s+System\s+$IHS$testing I need to make sure it only matches the whole phrase and not some string that starts with this phrase.

Paul Creasey Over a year ago

you could use \W which is the same as [^\w] or [^a-bA-B0-9_] (not sure exactly what it includes in java), or you could create you own character class (or negated class) to specify what does or does not indicate a match. I've updated the example with \W which will likely work pretty well.

Eqbal Over a year ago

Thanks, \W seems to work pretty well so far combined with grouping to extract the matched phrase minus the non-word character that follows.

bobince Over a year ago

If you want to allow the match at the end of the string you would have to say ($|\W). I'm not sure it's so important though, are you likely to have strings like Integrated Health Systems (IHS)foo? The close bracket is almost invariably followed by space or punctuation.

Eqbal Over a year ago

Okay, here is my final regex pattern: "(\\b|\\W)(" + phrase + ")($|\\W)" Using the group 2 to get the matched phrase.

|

cyborg · Accepted Answer · 2010-01-05 23:24:42Z

0

You've got (IHS) - a group - where you want $IHS$ as the literal brackets.

answered Jan 5, 2010 at 23:24

cyborg

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Comments

mopoke · Accepted Answer · 2010-01-05 23:24:57Z

0

You need to escape the parentheses

\bIntegrated\s+Health\s+System\s+\(IHS\)\b

Parentheses delimit a capture group. To match a literal set of parentheses, you can escape them like this 

answered Jan 5, 2010 at 23:24

mopoke

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1 Comment

tchrist Over a year ago

It isn’t safe to use \b in Java. It doesn’t mean what you think it does. See here for why.

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