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

r"
"
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]{0,2}\\[([\\d]*)\\]:"; final String string = "---\n" + " # Meta Data\n" + " Title: Test Set for Mark Down Reference Linking\n" + " Summary: Test Set for Mark Down Reference Linking\n" + " Author: Royi \n\n" + " # Settings\n" + " settings:\n" + " enable_uml: true\n" + " image_path_conversion: base64\n" + " markdown_extensions:\n" + " - markdown.extensions.footnotes\n" + " - markdown.extensions.fenced_code\n" + " - markdown.extensions.tables\n" + " - markdown.extensions.admonition\n" + " - markdown.extensions.toc:\n" + " title: Table of Contents\n" + " toc_depth: 2-3\n" + " - pymdownx.arithmatex:\n" + " generic: true\n" + " smart_dollar: false\n" + " allow_css_overrides: true\n" + "---\n\n\n" + "# Test Set for Mark Down Reference Linking\n\n" + "[TOC]\n\n" + "## Scope of the Document\n\n" + "Just some text as a test set.\n\n\n" + "### Some ASCII Graphics\n\n" + "Laser beam.\n\n" + "```\n" + " \n" + " Target \n" + " \n" + " +--------------------------------+ \n" + " | | \n" + " | | \n" + " | | \n" + " | | \n" + " | -- | \n" + " | -/ | \n" + " | --/ | \n" + " | -/ | \n" + " | --/ | \n" + " +--------------------------------+ \n" + " -/ \n" + " --/ \n" + " <-------------------/-----------------------> \n" + " --/ \n" + " -/ \n" + " --/ \n" + " +--------/ \n" + " | -/| \n" + " | -/ | \n" + " | | Laser Beam\n" + " +------+ \n" + "```\n\n" + "## Some List\n\n" + " * Train Set - Set used for training the ML model (For instance optimize the model parameters [For Parametric Model])\n" + " * Test Set - Set used to evaluate results.\n" + " * Prediction - Prediction of velocity given a measurement.\n\n" + "Implicit / Explicit Assumptions[^001]:\n\n" + " * The laser beam is eye safe.\n" + " * Just some information[^002].\n\n" + "### Some Existing Links\n\n" + "The results are pretty good in [RMSE][001] / [MAE][002].\n\n\n" + "## Some Text to Test\n\n" + "Free text, **bold text**, *italic text*, [__bold text__][003] or _italic text_.\n" + "Also, `Mono Spaced Text` and regular [boring text][04].\n\n" + "Some [Link](https://www.wikipedia.com) and [Reference Link][1].\n\n" + "Some list...\n\n" + " * Examining Deep Learning (DL) Based Methods \n" + " Always some text on [Deep][1] Learning.\n" + " * Hyper Parameters \n" + " Adding an exhaustive search of the optimal Hyper Parameters.\n\n\n" + " [001]: https://en.wikipedia.org/wiki/Root-mean-square_deviation \"Wikipedia - RMSE\"\n" + " [002]: https://en.wikipedia.org/wiki/Mean_absolute_error \"Wikipedia - MAE\"\n\n" + "[003]: https://something.com\n" + " [04]: https://somewhere.com\n\n" + " [5]: Should not be selected!\n" + " [6]: Should not be selected!\n\n\n" + " [^001]: Just a simple assumption reference.\n" + " [^002]: Just another simple assumption reference.\n\n\n\n\n" + "[1]: https://www.wikipedia.com"; 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