Re: regex for any word from a set of words

I presume the problem is to define a regular expression which returns
the entire content of a string for all strings not containing any of a
set of string literals.

 

How about this:

 

^((?:(?!foo)(?!bar)(?!baz).)+)$

 

Where:

 

^               # Anchor to beginning of string
  (             # Capture
   (?:          # Complex expression:
      (?!foo)  #   make sure we're not at the beginning of string
literal "foo" 
      (?!bar)  #     and we're not at the beginning of string literal
"bar"
      (?!baz)  #     and we're not at the beginning of string literal
"baz"
      .         #   accept any character
   )+           # at least once (to ensure string is not empty)
  )            # End capture
$              # anchor to end of string

 

-- Tim Uttormark

   Principal Java Architect, Peopleclick, Inc.

 

 

________________________________

From: [email protected] [mailto:[email protected]] On
Behalf Of Tim Jowers
Sent: Monday, April 21, 2008 10:01 AM
To: Java Users Group
Subject: [Juglist] regex for any word from a set of words

 


Hi,

I'm seeking to define a regular expression to match on one of a set of
words. Does anyone have a trick for this? Does anyone have a trick for
negative search (find all but strings having a word)?

Specifically, EMC Smarts network monitoring software allows subscription
to events based on a regular expression. We do not want noise events
like "Unresponsive" or "Duplicate".

To match all, I can use: 
.*
To match the ones I do NOT want I could use:
.*Unresponsive$  to find matches to with Unresponsive
.*[U|D][n|u][r|p][e|l][s|i][p|c][o|a][n|t]s?i?v?e"

But of course the last one also matches other letter combinations like
"Unplicate". :-) This could be OK for our scenario as we have defined a
small set of event types.

But what about NOT having a word. I've searched for this on the net for
about 1.5 hours and tried various things but does anyone know a good way
to write a regular expression to match any strings *without* a word from
a set of words?

I can contrive something to match anything except the word
"Unresponsive" for instance:
".+?_(?!U(?:n(?!r(?:e(?:s(?!p(?:o(?!s)))))))).+?"

Unfortunately, the "groups" created with parenthesis really are not much
use in Pattern.matches but only when iterating for matches. E.g. I can
find matches with:
    String regex = ".+?com_(?!Unresponsive)";
    Pattern pattern = Pattern.compile(regex);
    Matcher matcher = pattern.matcher(candidateString);
    while (matcher.find()) {
      System.out.println("MATCH:" + matcher.group() );
    }
The (?!  signifies the negative search and works fine for making groups
but does not seem to work for testing if an expression matches or not. I
can try the ^ operator but like everything else it only seems to apply
to the next character.

My reasoning is the regular expression logic creates a match graph based
on characters so any "word" matching really has to be distilled to
character matching which make the use of a Regular Expression for this
task a tedious challenge at best and error prone at least. Has anyone
found a class or library with a Regular Expression style functionality
but operating on Strings? Or Strings as well as characters?


Thanks!
TimJowers

_______________________________________________
Juglist mailing list
[email protected]
http://trijug.org/mailman/listinfo/juglist_trijug.org