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

/
/
gxJm

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 = "# SETTINGS\n" + " (?<ANCHORED>){1}\n" + " (?<NO_SIGN_DUP>){1}\n" + " (?<PYTHON_POW>){1}\n" + " (?<COMMENTS>){0}\n\n" + "(?(ANCHORED)^(?&s)*)\n" + "(?(DEFINE)\n" + " (?<s>(?(COMMENTS)(?:\\s+|\\/\\*[\\s\\S]*?\\*\\/|\\/\\/.*|\\#.*)|\\s+))\n" + " (?<sign>(?(NO_SIGN_DUP)(?<=(?<_>[\\s\\S]))(?!(?P=_)))[-+])\n" + " (?<base>\\d+(?:\\.\\d*)?|\\d*\\.\\d+)\n" + " (?<exp>(?:[eE][+-]?\\d+))\n" + " (?<num>(?&sign)?(?&base)(?&exp)?(?!\\w))\n" + " (?<bracketed>\\((?&s)*(?&expr)(?&s)*\\))\n" + " (?<atom>(?&num)|(?&bracketed))\n" + " (?<pow>(?&atom)(?:(?&s)*(?(PYTHON_POW)(?:\\^|\\*\\*)|\\^)(?&s)*(?&pow))*)\n" + " (?<mul>(?&pow)(?:(?&s)*[*\\/](?&s)*(?&mul))*)\n" + " (?<add>(?&mul)(?:(?&s)*[+-](?&s)*(?&add))*)\n" + " (?<expr>(?&add))\n" + ")\n" + "(?&expr)\n" + "(?(ANCHORED)(?&s)*$)"; final String string = "0\n" + "::\n" + "1\n" + "::\n" + "+1\n" + "::\n" + "-1\n" + "::\n" + "1.e-1\n" + "::\n" + "1e1\n" + "::\n" + ".1e+1\n" + "::\n" + "-6*((2**(2+4))/3)\n" + "::\n" + "0*0\n" + "::\n" + "0+0\n" + "::\n" + "0/0\n" + "::\n" + "0^0\n" + "::\n" + "0**0\n" + "::\n" + "0-0\n" + "::\n" + "5 - -2\n" + "::\n" + "5- -2\n" + "::\n" + "5+-2\n" + "::\n" + ".1\n" + "::\n" + "1.\n" + "::\n" + "1.1\n" + "::\n" + " -2\n" + "::\n" + "5 * (2 + 5 /* comment */ // )\n" + " - 1)\n\n" + "INVALID: // Separated by :: to prevent parsing multiple examples\n" + ".\n" + "::\n" + "1e\n" + "::\n" + "1e+\n" + "::\n" + "1e-\n" + "::\n" + "e2\n" + "::\n" + "+\n" + "::\n" + "-\n" + "::\n" + "5 --2\n\n"; final Pattern pattern = Pattern.compile(regex, Pattern.COMMENTS | 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