Regular Expressions 101

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  • Unit Tests (2)

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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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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

/
/
gm

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 = "^(?:(?:25[0-5]|2[0-4]\\d|1?\\d{1,2})(?:\\.(?!$)|$)){4}$"; final String string = "validates:\n" + "192.68.35.35\n" + "0.0.0.0\n" + "255.0.0.0\n" + "192.168.1.0\n" + "192.168.0.1\n" + "255.255.255.0\n" + "1.1.1.1\n" + "255.255.255.255\n" + "249.249.249.249\n" + "200.200.200.200\n" + "199.199.199.199\n" + "100.100.100.100\n" + "99.99.99.99\n" + "0.0.0.0\n" + "9.9.9.9\n" + "10.10.10.10\n" + "99.99.99.99\n" + "100.100.100.100\n" + "109.109.109.109\n" + "110.110.110.110\n" + "199.199.199.199\n" + "200.200.200.200\n" + "249.249.249.249\n" + "250.250.250.250\n" + "255.255.255.255\n" + "01.01.01.01\n" + "09.09.09.09\n" + "192.168.0.1\n" + "255.255.255.255\n" + "1.1.1.1\n\n" + "should not validate:\n" + "256.256.256.260\n" + "192.168.0.0/24\n" + "192.168..1\n" + "192.168.1\n" + "1\n" + "1.\n" + "1.1\n" + "1.1.\n" + "1.1.1\n" + "1.1.1.\n" + "1.1.1.1.\n" + "1.1.1.1.1\n" + ".1.1.1.1\n" + "1.0.0.1.0\n" + "010.1.1.1\n" + "123456\n" + "123123123123\n" + ".127.0.0.1\n" + "192.168.0.1000\n" + "300.168.0.1\n" + "192.168.0.1.\n" + "192.168.0..1\n" + "192.16a8.0.1\n" + "123.234.345\n" + "123.123\n" + "11.11.1\n" + ".192.168.0.1\n" + ".192.168.0.\n" + ".192.168.0\n" + "....\n" + ".......\n" + "........"; final Pattern pattern = Pattern.compile(regex, 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