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

`
`
gmx

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 = "^\n" + "(?(DEFINE)\n" + " (?<hex4>[0-9A-Fa-f]{1,4})\n" + " (?<hex4_>(?&hex4):)\n" + " (?<_hex4>:(?&hex4))\n" + " (?<byte>\n" + " (25[0-5])|(2[0-4]\\d)|(1\\d{2})|([1-9]\\d)|\\d\n" + " )\n" + " (?<ipv4>\n" + " ((?&byte)\\.){3}(?&byte)\n" + " )\n" + ")\n" + "(((?&hex4_){7}(?&hex4))\n" + "|((?&hex4_){5}(?&_hex4))\n" + "|((?&hex4_){4}(?&_hex4){1,2})\n" + "|((?&hex4_){3}(?&_hex4){1,3})\n" + "|((?&hex4_){2}(?&_hex4){1,4})\n" + "|((?&hex4_){1}(?&_hex4){1,5})\n" + "|(:(?&_hex4){1,6})\n" + "|((?&hex4_){1,6}:)\n" + "|((?&hex4_){6}(?&ipv4))\n" + "|((?&hex4_){3}(?&_hex4):(?&ipv4))\n" + "|((?&hex4_){2}(?&_hex4){1,2}:(?&ipv4))\n" + "|((?&hex4_){1}(?&_hex4){1,3}:(?&ipv4))\n" + "|((?&hex4_){1,4}:(?&ipv4))\n" + "|(:(?&_hex4){0,4}:(?&ipv4))\n" + ")$"; final String string = ";valid\n" + "2001:db8:0:0:0:0:2:1\n" + "2001:db8::2:1\n" + "2001:db8:0:1:1:1:1:1\n" + "2001:db8:a0b:12f0::1\n" + "2001:0db8:0a0b:12f0:0000:0000:0000:0001\n" + "3731:54:65fe:2::a7\n" + "::10.0.0.3\n" + "::ffff:0:10.0.0.3\n" + "0064:ff9b:0000:0000:0000:0000:18.52.86.120\n" + "0064:ff9b::0000:18.52.86.120\n" + "0064:ff9b::18.52.86.120\n\n" + ";invalid\n" + "2001:db8::1:1:1:1:1\n" + "10.0.0.3\n" + "::256.127.0.1\n" + "::127.0.0.01\n" + "::127.0.0\n"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE | Pattern.COMMENTS); 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