Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

/
/
igm

Test String

Code Generator

Language

Generated Code

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = "(?:^|\\s)(([0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]+|::(ffff(:0{1,4})?:)?((25[0-5]|2[0-4]\\d|1\\d{0,2}|[1-9]?\\d)\\.){3}(25[0-5]|2[0-4]\\d|1\\d{0,2}|[1-9]?\\d)|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|2[0-4]\\d|1\\d{0,2}|[1-9]?\\d)\\.){3}(25[0-5]|2[0-4]\\d|1\\d{0,2}|[1-9]?\\d))(?=\\s|$)\n"; final String string = "{1: Initial address, regex should say valid/match}\n" + "2001:0db8:0000:0000:0000:ff00:0042:8329\n\n" + "{2: After removing all leading zeroes, regex should say valid/match}\n" + "2001:db8:0:0:0:ff00:42:8329\n\n" + "{3: After omitting consecutive sections of zeroes, regex should say valid/match}\n" + "2001:db8::ff00:42:8329\n\n" + "{4: The loopback address, regex should say valid/match}\n" + "0000:0000:0000:0000:0000:0000:0000:0001\n\n" + "{5: The loopback address be abbreviated to ::1 by using both rules, regex should say valid/match}\n" + "::1\n\n" + "{6: This should be valid, regex should say valid/match}\n" + "ABCD:ABCD:ABCD:ABCD:ABCD:ABCD:192.168.158.190\n\n" + "{7: This should NOT be valid/match}\n" + "::\n\n" + "{These two formats allows IPv6 applications to communicate directly with IPv4 applications, regex should say valid/match}\n" + "{8}\n" + "0:0:0:0:0:ffff:192.1.56.10\n" + "{9}\n" + "::ffff:192.1.56.10/96\n\n" + "{These next two formats are used for tunneling. It allows IPv6 nodes to communicate across an IPv4 infrastructure, regex should say valid/match}\n" + "{10}\n" + "0:0:0:0:0:0:192.1.56.10\n" + "{11}\n" + "::192.1.56.10/96\n\n" + "{These 4 should be valid/match}\n" + "{12}\n" + "::FFFF:129.144.52.38\n" + "{13}\n" + "::129.144.52.38\n" + "{14}\n" + "::FFFF:d\n" + "{15}\n" + "1080:0:0:0:8:800:200C:417A\n\n" + "{These 4 should NOT be valid/match}\n" + "{16}\n" + "::FFFF:d.d.d\n" + "{17}\n" + "::FFFF:d.d\n" + "{18}\n" + "::d.d.d\n" + "{19}\n" + "::d.d"; final Pattern pattern = Pattern.compile(regex, Pattern.CASE_INSENSITIVE | Pattern.MULTILINE); final Matcher matcher = pattern.matcher(string); while (matcher.find()) { System.out.println("Full match: " + matcher.group(0)); for (int i = 1; i <= matcher.groupCount(); i++) { System.out.println("Group " + i + ": " + matcher.group(i)); } } } }

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Java, please visit: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html