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 = "# Leap Years are any year that can be evenly divided by 4 \n" + "# (such as 2012, 2016, etc)\n" + "# • except if it can be evenly divided by 100\n" + "# then it isn't (such as 2100, 2200, etc)\n" + "# • except if it can be evenly divided by 400,\n" + "# then it is (such as 2000, 2400)\n" + "# https://www.mathsisfun.com/leap-years.html\n" + "# -------------------------------------------------\n" + "# verify date dd/mm/yyyy; possible separators: -.,/\n" + "# valid year range: 0000-9999\n\n" + "^ # start anchor\n\n" + "# precheck xx-xx-xxxx,... add new separators here\n" + "(?=\\d{2}([-.,\\/])\\d{2}\\1\\d{4}$)\n\n" + "(?: # day-check: non caturing group\n\n" + " # days 01-28\n" + " 0[1-9]|1\\d|[2][0-8]| \n\n" + " # february 29d check for leap year: all 4y / 00 years: only each 400\n" + " # 0400,0800,1200,1600,2000,...\n" + " 29\n" + " (?!.02. # not if feb: if not ...\n" + " (?!\n" + " # 00 years: exclude !0 %400 years\n" + " (?!(?:[02468][1-35-79]|[13579][0-13-57-9])00)\n\n" + " # 00,04,08,12,... \n" + " \\d{2}(?:[02468][048]|[13579][26])\n" + " )\n" + " )|\n\n" + " # d30 negative lookahead: february cannot have 30 days\n" + " 30(?!.02)|\n\n" + " # d31 positive lookahead: month up to 31 days\n" + " 31(?=.(?:0[13578]|10|12))\n\n" + ") # eof day-check\n\n" + "# month 01-12\n" + ".(?:0[1-9]|1[012])\n\n" + "# year 0000-9999\n" + ".\\d{4}\n\n" + "$ # end anchor"; final String string = "29/02/0000\n" + "29/02/0100\n" + "29/02/0200\n" + "29/02/0300\n" + "29/02/0400\n" + "29/02/0500\n" + "29/02/0600\n" + "29/02/0700\n" + "29/02/0800\n" + "29/02/0900\n" + "29/02/1000\n" + "29/02/1100\n" + "29/02/1200\n" + "29/02/1300\n" + "29/02/1400\n" + "29/02/1500\n" + "29/02/1600\n" + "29/02/1700\n" + "29/02/1800\n" + "29/02/1900\n" + "29/02/2000\n" + "29/02/2100\n" + "29/02/2200\n" + "29/02/2300\n" + "29/02/2400\n" + "29/02/2500"; 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