I have the following aaaa_bb_cc string to match and written a regex pattern like
\\w{4}+\\_\\w{2}\\_\\w{2} and it works. Is there any simple regex which can do this same ?
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1Yours is really simple, for a regular expression. =)Jens– Jens2010-05-06 11:54:29 +00:00Commented May 6, 2010 at 11:54
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4 Answers
You don't need to escape the underscores:
\w{4}+_\w{2}_\w{2}
And you can collapse the last two parts, if you don't capture them anyway:
\w{4}+(?:_\w{2}){2}
Doesn't get shorter, though.
(Note: Re-add the needed backslashes for Java's strings, if you like; I prefer to omit them while talking about regular expressions :))
1 Comment
ukanth
Yes. I can understand that ;)
I sometimes do what I call "meta-regexing" as follows:
String pattern = "x{4}_x{2}_x{2}".replace("x", "[a-z]");
System.out.println(pattern); // prints "[a-z]{4}_[a-z]{2}_[a-z]{2}"
Note that this doesn't use \w, which can match an underscore. That is, your original pattern would match "__________".
If x really needs to be replaced with [a-zA-Z0-9], then just do it in the one place (instead of 3 places).
Other examples
answered May 6, 2010 at 12:07
polygenelubricants
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1 Comment
polygenelubricants
@UK: Essentially the idea is that you don't need to have the actual regex explicitly written out. If it makes it more readable/maintainable to derive the regex programmatically, then go ahead
Yes, you can use just \\w{4}_\\w{2}_\\w{2} or maybe \\w{4}(_\\w{2}){2}.
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Looks like your \w does not need to match underscore, so you can use [a-zA-Z0-9] instead
[a-zA-Z0-9]{4}_[a-zA-Z0-9]{2}_[a-zA-Z0-9]{2}
1 Comment
Joey
Missed that one. However, is
\w in Java really only [a-zA-Z0-9]? In .NET at least both \d and \w match pretty much anything counting as decimal number or letter.