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
No Match

@"
"
gm

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 = "^[a-z][a-z0-9]*(([A-Z]{1,3}[a-z0-9]+)*[A-Z]{0,3}|([a-z0-9]+[A-Z]{1,3})*|[A-Z]{1,3})$"; final String string = "snake_case\n" + "PascalCase\n" + "2PascalCase\n" + "streamIOIO\n" + "gREATERDtha\n" + "modeADFAFdsADFads\n" + "aBabcABCDabcABC\n" + "camelCa_1\n" + "contextHTMLParser\n" + "hELLO\n" + "modeADFdsADFads\n" + "streamIO\n" + "aBCabcABCabcA\n" + "aBCabcA\n" + "aabc123\n" + "aabcABC\n" + "ab\n" + "abc\n" + "abcd\n" + "abcde\n" + "deviceSNS\n" + "pathASNs\n" + "dscpCP\n" + "awsVPC\n" + "deviceID\n" + "camelCasecamelCasecamelCasecamelCasecamelCasecamelCase\n" + "gREA1\n" + "gREAt\n" + "gREAtREAt\n" + "cP3\n" + "a1\n" + "aABC\n" + "a123\n" + "modeADFsADFads\n" + "a1G\n" + "aG\n" + "a\n" + "modeADFads\n" + "camelCase\n" + "lThan30DaysCount\n" + "lessThan30DaysCount\n" + "lessThan30DaysCountA\n" + "greaterThan30LessThan60DaysCount\n" + "greaterThan60LessThan90DaysCount\n" + "greaterThan90DaysCount\n" + "pascalCase\n" + "pascal2Case\n" + "pascalCaseA\n" + "pascal2CaseA\n" + "modeA\n" + "mode2A\n" + "mode2A2\n" + "mode2A2A\n" + "createAMode\n" + "createBMode\n" + "madeEasy\n" + "wonderFul\n" + "andMe\n" + "htmlParser\n" + "h\n" + "aaA\n" + "camel01C\n" + "camel01c01\n" + "camel01C01\n" + "camel01CC01\n" + "camel0a1c1\n" + "camel0a1C1\n" + "camel0ac1b1C1\n" + "camelC\n" + "camelC1\n" + "camelCA\n" + "camelCa1\n" + "ibsReleaseTestVerificationRegressionSuite\n" + "ibsReleaseTestVerificationRegressioNSuite\n" + "ibsReleaseTestVerificationRegressioN\n" + "xmlHttpRequest\n" + "newCustomerId\n" + "innerStopwatch\n" + "supportsIpv6OnIos\n" + "youTubeImporter\n" + "youtubeImporter\n" + "affine3D"; 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