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

/
/
mixg

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 = "(?(DEFINE)\n" + " (?<tagnames> @CUSTOM-AT-1 | @CUSTOM-AT-2)\n" + " (?<number> -? (?= [1-9]|0(?!\\d) ) \\d+ (\\.\\d+)? ([eE] [+-]? \\d+)? )\n" + " (?<boolean> true | false | null )\n" + " (?<string> \\\" ([^\\\"\\\\\\\\]* | \\\\\\\\ [\\\"\\\\\\\\bfnrt\\/] | \\\\\\\\ u [0-9a-f]{4} )* \\\" )\n" + " (?<array> \\[ (?: (?&json) (?: , (?&json) )* )? \\s* \\] )\n" + " (?<pair> \\s* (?&string) \\s* : (?&json) )\n" + " (?<object> \\{ (?: (?&pair) (?: , (?&pair) )* )? \\s* \\} )\n" + " (?<fieldname> [a-zA-Z0-9\\_\\-]+ )\n" + " (?<json> \\s* (?: (?&number) | (?&boolean) | (?&string) | (?&array) | (?&object) ) )\n" + " (?<fieldlist> (?: (?&fieldname) (?: , (?&fieldname) )+ )+ ) )\n" + " (?<actiontag> (?&tagnames)\n" + ")\n" + "(?:\\=\n" + " (?'params'\n" + " (?:\n" + " (?'match_list'(?&fieldlist))\n" + " |\n" + " (?'match_json'(?&json))\n" + " |\n" + " (?'match_string'(?:[[:alnum:]\\_\\-]+))\n" + " )\n" + " )\n" + ")"; final String string = "@FIELDLIST=field_1,field_2\n\n\n" + "@STRING=\"Bar\"\n\n\n" + "@JSON={\"foo\":\"bar\"}\n\n\n" + "@CUSTOM-AT-2={\"strict\":true, \"targets\":[\"field_3\", \"field_7\"], \"title\":\"Custom Title\", \"message\":\"This is a custom message\"}\n\n" + "@CUSTOM-AT-1={\"strict\":true, \"targets\":[\"field_3\", \"field_7\"], \"title\":\"Custom Title\", \"message\":\"This is a custom message\"}"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE | Pattern.CASE_INSENSITIVE | 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