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

/
/
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 = "^##\\s\\[?(Unreleased)\\]?|^##\\s\\[((0|[1-9]\\d*)\\.(0|[1-9]\\d*)\\.(0|[1-9]\\d*)(?:-((?:0|[1-9]\\d*|\\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\\.(?:0|[1-9]\\d*|\\d*[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\\+([0-9a-zA-Z-]+(?:\\.[0-9a-zA-Z-]+)*))?)\\]$"; final String string = "Valid Semantic Versions\n\n" + "## [Unreleased]\n" + "## Unreleased\n" + "## foo\n" + "## [foo]\n\n" + "## [0.0.4]\n" + "## [1.2.3]\n" + "## [10.20.30]\n" + "## [1.1.2-prerelease+meta]\n" + "## [1.1.2+meta]\n" + "## [1.1.2+meta-valid]\n" + "## [1.0.0-alpha]\n" + "## [1.0.0-beta]\n" + "## [1.0.0-alpha.beta]\n" + "## [1.0.0-alpha.beta.1]\n" + "## [1.0.0-alpha.1]\n" + "## [1.0.0-alpha0.valid]\n" + "## [1.0.0-alpha.0valid]\n" + "## [1.0.0-alpha-a.b-c-somethinglong+build.1-aef.1-its-okay]\n" + "## [1.0.0-rc.1+build.1]\n" + "## [2.0.0-rc.1+build.123]\n" + "## [1.2.3-beta]\n" + "## [10.2.3-DEV-SNAPSHOT]\n" + "## [1.2.3-SNAPSHOT-123]\n" + "## [1.0.0]\n" + "## [2.0.0]\n" + "## [1.1.7]\n" + "## [2.0.0+build.1848]\n" + "## [2.0.1-alpha.1227]\n" + "## [1.0.0-alpha+beta]\n" + "## [1.2.3----RC-SNAPSHOT.12.9.1--.12+788]\n" + "## [1.2.3----R-S.12.9.1--.12+meta]\n" + "## [1.2.3----RC-SNAPSHOT.12.9.1--.12]\n" + "## [1.0.0+0.build.1-rc.10000aaa-kk-0.1]\n" + "## [99999999999999999999999.999999999999999999.99999999999999999]\n" + "## [1.0.0-0A.is.legal]\n\n\n\n" + "Invalid Semantic Versions\n\n" + "## [1]\n" + "## [1.2]\n" + "## [1.2.3-0123]\n" + "## [1.2.3-0123.0123]\n" + "## [1.1.2+.123]\n" + "## [+invalid]\n" + "## [-invalid]\n" + "## [-invalid+invalid]\n" + "## [-invalid.01]\n" + "## [alpha]\n" + "## [alpha.beta]\n" + "## [alpha.beta.1]\n" + "## [alpha.1]\n" + "## [alpha+beta]\n" + "## [alpha_beta]\n" + "## [alpha.]\n" + "## [alpha..]\n" + "## [beta]\n" + "## [1.0.0-alpha_beta]\n" + "## [-alpha.]\n" + "## [1.0.0-alpha..]\n" + "## [1.0.0-alpha..1]\n" + "## [1.0.0-alpha...1]\n" + "## [1.0.0-alpha....1]\n" + "## [1.0.0-alpha.....1]\n" + "## [1.0.0-alpha......1]\n" + "## [1.0.0-alpha.......1]\n" + "## [01.1.1]\n" + "## [1.01.1]\n" + "## [1.1.01]\n" + "## [1.2]\n" + "## [1.2.3.DEV]\n" + "## [1.2-SNAPSHOT]\n" + "## [1.2.31.2.3----RC-SNAPSHOT.12.09.1--..12+788]\n" + "## [1.2-RC-SNAPSHOT]\n" + "## [-1.0.3-gamma+b7718]\n" + "## [+justmeta]\n" + "## [9.8.7+meta+meta]\n" + "## [9.8.7-whatever+meta+meta]\n" + "## [99999999999999999999999.9"; 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