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

/
/
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 = "^((0?[1-9]|[12][0-9]|3[01])(Jan|JAN|Mar|MAR|May|MAY|Jul|JUL|Aug|AUG|Oct|OCT|Dec|DEC)([0-9][0-9][0-9][0-9])|(0?[1-9]|[12][0-9]|30)(Apr|APR|Jun|JUN|Sep|SEP|Nov|NOV)([0-9][0-9][0-9][0-9])|(0?[1-9]|1[0-9]|2[0-8])(Feb|FEB)([0-9][0-9][0-9][0-9])|(29)(Feb|FEB)([0-9][0-9])([02468][048]|[13579][26]))$"; final String string = "1Jan2018 abcd\n" + "1Jan18\n" + "01Jan18\n" + "1Jan2018\n" + "01Jan2018\n" + "31Jan2018\n" + "31jan2018\n" + "31jAN2018\n" + "31JaN2018\n" + "31JAn2018\n" + "31JAN2018\n" + "28Feb2018\n" + "29Feb2018\n" + "29Feb2020\n" + "31Mar2018\n" + "30Apr2018\n" + "31Apr2018\n" + "31May2018\n" + "30Jun2018\n" + "31Jun2018\n" + "31Jul2018\n" + "31Aug2018\n" + "30Sep2018\n" + "31Sep2018\n" + "31Oct2018\n" + "30Nov2018\n" + "31Nov2018\n" + "31Dec2018"; 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