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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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

/
/
gm

Test String

Code Generator

Generated Code

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = "(?x) # free-spacing mode\n" + "(?(DEFINE)\n" + " # Within this DEFINE block, we'll define many subroutines\n" + " # They build on each other like lego until we can define\n" + " # a \"big number\"\n\n" + " (?<one_to_9> \n" + " # The basic regex:\n" + " # one|two|three|four|five|six|seven|eight|nine\n" + " # We'll use an optimized version:\n" + " # Option 1: four|eight|(?:fiv|(?:ni|o)n)e|t(?:wo|hree)|\n" + " # s(?:ix|even)\n" + " # Option 2:\n" + " (?:f(?:ive|our)|s(?:even|ix)|t(?:hree|wo)|(?:ni|o)ne|eight)\n" + " ) # end one_to_9 definition\n\n" + " (?<ten_to_19> \n" + " # The basic regex:\n" + " # ten|eleven|twelve|thirteen|fourteen|fifteen|sixteen|seventeen|\n" + " # eighteen|nineteen\n" + " # We'll use an optimized version:\n" + " # Option 1: twelve|(?:(?:elev|t)e|(?:fif|eigh|nine|(?:thi|fou)r|\n" + " # s(?:ix|even))tee)n\n" + " # Option 2:\n" + " (?:(?:(?:s(?:even|ix)|f(?:our|if)|nine)te|e(?:ighte|lev))en|\n" + " t(?:(?:hirte)?en|welve)) \n" + " ) # end ten_to_19 definition\n\n" + " (?<two_digit_prefix>\n" + " # The basic regex:\n" + " # twenty|thirty|forty|fifty|sixty|seventy|eighty|ninety\n" + " # We'll use an optimized version:\n" + " # Option 1: (?:fif|six|eigh|nine|(?:tw|sev)en|(?:thi|fo)r)ty\n" + " # Option 2:\n" + " (?:s(?:even|ix)|t(?:hir|wen)|f(?:if|or)|eigh|nine)ty\n" + " ) # end two_digit_prefix definition\n\n" + " (?<one_to_99>\n" + " (?&two_digit_prefix)(?:[- ](?&one_to_9))?|(?&ten_to_19)|\n" + " (?&one_to_9)\n" + " ) # end one_to_99 definition\n\n" + " (?<one_to_999>\n" + " (?&one_to_9)[ ]hundred(?:[ ](?:and[ ])?(?&one_to_99))?|\n" + " (?&one_to_99)\n" + " ) # end one_to_999 definition\n\n" + " (?<one_to_999_999>\n" + " (?&one_to_999)[ ]thousand(?:[ ](?&one_to_999))?|\n" + " (?&one_to_999)\n" + " ) # end one_to_999_999 definition\n\n" + " (?<one_to_999_999_999>\n" + " (?&one_to_999)[ ]million(?:[ ](?&one_to_999_999))?|\n" + " (?&one_to_999_999)\n" + " ) # end one_to_999_999_999 definition\n\n" + " (?<one_to_999_999_999_999>\n" + " (?&one_to_999)[ ]billion(?:[ ](?&one_to_999_999_999))?|\n" + " (?&one_to_999_999_999)\n" + " ) # end one_to_999_999_999_999 definition\n\n" + " (?<one_to_999_999_999_999_999>\n" + " (?&one_to_999)[ ]trillion(?:[ ](?&one_to_999_999_999_999))?|\n" + " (?&one_to_999_999_999_999)\n" + " ) # end one_to_999_999_999_999_999 definition\n\n" + " (?<bignumber>\n" + " zero|(?&one_to_999_999_999_999_999)\n" + " ) # end bignumber definition\n\n" + " (?<zero_to_9>\n" + " (?&one_to_9)|zero\n" + " ) # end zero to 9 definition\n\n" + " (?<decimals>\n" + " point(?:[ ](?&zero_to_9))+\n" + " ) # end decimals definition\n" + " \n" + ") # End DEFINE\n\n\n" + "####### The Regex Matching Starts Here ########\n" + "^(?&bignumber)(?:[ ](?&decimals))?$\n\n" + "### Other examples of groups we could match ###\n" + "#(?&bignumber)\n" + "# (?&one_to_99)\n" + "# (?&one_to_999)\n" + "# (?&one_to_999_999)\n" + "# (?&one_to_999_999_999)\n" + "# (?&one_to_999_999_999_999)\n" + "# (?&one_to_999_999_999_999_999)"; final String string = "one trillion\n" + "seven hundred twenty two\n" + "7even\n" + "zero point nine five\n" + "nine hundred ninety nine thousand two hundred thirteen"; 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