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Oct 21, 2011 · Writing a simple regex, but I've never been very good at this. What I'm trying to do is check a string (filename) to make sure it only contains a-z, A-Z, 0-9 or the special characters underscore (_) period (.) or dash (-). Here's what I have. return false; return true; This appears to work, but does not look very elegant to me.
This is a valid regex for validating e-mails. It's totally compliant with RFC822 and accepts IP address and server names (for intranet purposes).
Nov 28, 2012 · To match the strings one OR other, use: or if you don't want to store the matches, just simply. To be Java specific, this article is very good at explaining the subject. You will have to use your patterns this way: String matchedString = myStrin.substring(matcher.start(),matcher.end());
The Java API for regular expressions states that \s will match whitespace. So the regex \\s\\s should match two spaces. Pattern whitespace = Pattern.compile("\\s\\s"); matcher = whitespace.matcher(modLine); while (matcher.find()) matcher.replaceAll(" "); The aim of this is to replace all instances of two consecutive whitespace with a single space.
String validIpPattern = zeroTo255 + "\\." + zeroTo255 + "\\." + zeroTo255 + "\\." + zeroTo255; (0|1)\d {2} catches any three digit number starting with 0 or 1. 2 [0-4]\d catches numbers between 200 and 249. 25 [0-5] catches numbers between 250 and 255. \d {1,2} catches any one or two digit number.
Jan 26, 2015 · 7. . symbol matches any character except newline. * repeats the character behind it 0 or more times. \d matches any digit. The extra \ in \\d is used to escape the backslash from the string. So .\\d. matches any single character, a digit, and any single character. It will match the following: a1b, p3k, &2@.
Apr 7, 2023 · might be better. If you need all three parts, this will do: "(\\D+)(\\d+)(.*)" EDIT The Expressions given by Allain and Jack suggest that you need to specify some subset of non-digits in order to capture digits. If you tell the regex engine you're looking for \d then it's going to ignore everything before the digits.
47. Parenthesis () are used to enable grouping of regex phrases. The group(1) contains the string that is between parenthesis (.*) so .* in this case. And group(0) contains whole matched string. If you would have more groups (read (...) ) it would be put into groups with next indexes (2, 3 and so on).
Dec 8, 2018 · If efficiency were a consideration, would be better off coding the operation by hand instead of using regex's, rather than accept the efficiency gain of capturing vs. non capturing groups. IMO, the decision of whether to use capturing vs. non capturing should simply document the intent of the expression.
The lines are probably separated by \r\n in your file. Both \r (carriage return) and \n (linefeed) are considered line-separator characters in Java regexes, and the . metacharacter won't match either of them. \s will match those characters, so it consumes the \r, but that leaves .* to match the \n, which fails.
