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

/
/
g

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])[\\x09\\x20]*(?:\\/(?![*+?])(?:(?:[^\\n\\[\\\\\\/]*+(?:\\\\\\\\)*+(?:\\\\\\[|\\\\\\/|\\\\(?!\\[))?(\\[)?)+(?(1)([^\\n\\]\\\\]*+(\\\\\\\\)*+(\\\\\\]|\\\\(?!\\]))?)*((?<!\\\\)\\])?))*[^\\n]*?(?<![^\\\\]\\/)(?<![^\\\\]\\\\)\\/)[gim]{0,3}[\\x09\\x20]*+(?![^\\}\\]\\),;:.\\n])"; final String string = "// Regular expressions \n" + " r = /([\\\\/])?([^\\\\/]*)$/; \n" + " r = /([\\\\/])?([^\\\\:/]*)$/; // коммент \n" + " /abc\\[def\\[^\\s[\\]/]ghi/g.test(s);// здесь одна пара квадратных скобок! \n" + "r = /\\//i; \n" + " r = /[/\\*]/img; // коммент \n" + " r = /[a-z]{5}/; \n" + " r = /[a-z]{1,5}/; \n" + " r = /([a-z])+/; \n" + " r = /([a-z]{1,5})+/; \n" + "r = /f([a-z])/; \n" + "r = /f([a-z]+)*/; \n" + "r = /a(b)c(d)/; \n" + "r = /a(b)?c(d)+?/; \n" + "r =(t|/\\*/.test(s)); \n" + " r =(t|/\\*/); // коммент \n" + "r =/./.test(s) && f(); \n" + "r=/[a-z]/.test(s) && f(); \n" + "var a = [/a\\/, \\/b/]; \n" + " a=[/a/,/b/]; \n" + "var o = { r: /./, x: 2 }; // коммент \n" + " o={r:/./,x:2}; \n" + "var x = a && /b/.test(s); \n" + " x = a ? /b/ : /c/;// коммент \n" + " x=a?/b/:/c/; \n" + " x=a?/b\\\\/:/c\\/\\\\/; // коммент \n" + " x=a?/b\\\\/:/c\\/\\\\/; // коммент \n" + " x = !/a/.test(s); \n" + " x = f(/./i); \n" + " x=1*s.replace(/^[^\\d]*(\\d+).*$/,'$1')/2; \n" + " /\\s\\n\\s+\\/\\/\\\\\\\\/.test(s)?f(null):f(/\\\\/); \n" + " /\\s\\n\\s+\\/\\/\\\\\\\\/.test(s)?f(null):f(/\\\\fghj[\\[fghj\\]]kl/), /fght/; \n" + " a=s.search(/\\s\\n\\s+\\/f\\//gi); \n" + " r=/>\\.jjj\\n<\\s\\</ \n" + " .exec(s); \n" + " r=/ \\n \\s/g, \n" + " t=/'/g \n" + " ; \n" + " \n" + "// Not a regular expressions \n" + "var n = 1/2;// коммент \n" + " n = 1/2/3; \n" + " n = 1/2/p; \n" + " n = 1/(2/p); // коммент \n" + " n = 1/this.n/3; \n" + " n = 1/this.f(5+4)/3; \n" + " n = 1/this.f(2/3); \n" + " n = 1/2 + (function() { return 3/4; })(); \n" + " n = 1/2*(this.x/3 + 2); \n" + " n = 1/2*(this.x + 2/3); \n" + " n =p/2,t=3/p; \n" + " n = f(1/2) + f(3/2);"; final Pattern pattern = Pattern.compile(regex); 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