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

/
/
g

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 = " *(?:.*\\S.*\\n)+\\n? *: +(?:.|\\n)+?(?:\\n{2,}(?=\\S)(?! *: +)(?! *(?:\\S.*\\n)+?\\n? *: +)|$)"; final String string = "=== Single <dt> and <dd>\n\n" + "GitHub\n" + ": a site where over 73 million developers shape the future of software, together\n\n" + "=== Multiple <dt>-<dd> group\n\n" + "Firefox\n" + ": a free, open source, cross-platform, graphical web browser developed by the Mozilla Corporation and hundreds of volunteers\n\n" + "MDN\n" + ": provides information about Open Web technologies including HTML, CSS, and APIs for both Web sites and progressive web apps\n\n" + "=== Single <dt> with multiple <dd>s\n\n" + "Apple\n" + " : an American multinational technology company that specializes in consumer electronics, computer software and online services.\n" + " : an edible fruit produced by an apple tree\n\n" + "=== Multiple <dt>s\n\n" + "Windows\n" + "Microsoft Windows\n" + "Win\n" + ": a group of several proprietary graphical operating system families, all of which are developed and marketed by Microsoft\n\n" + "=== separated by blank lines\n\n" + "Solaris\n\n" + ": a 1961 science fiction novel by Polish writer Stanisław Lem\n\n\n\n" + ": a proprietary Unix operating system originally developed by Sun Microsystems\n\n" + "=== <dd>s with inline breaks\n\n" + "Oracle\n" + ": an American multinational computer technology\n" + "corporation headquartered in Austin, Texas\n\n" + ": the priest or priestess uttering the prediction,\n" + "may also refer to the site of the oracle\n\n" + "===\n\n" + "😂\n" + ": 😂 face with tears of joy\n\n" + "===\n\n" + "Term 1\n\n" + ": This is a definition with two paragraphs. Lorem ipsum \n" + " dolor sit amet, consectetuer adipiscing elit. Aliquam \n" + " hendrerit mi posuere lectus.\n\n" + " Vestibulum enim wisi, viverra nec, fringilla in, laoreet\n" + " vitae, risus.\n\n" + ": Second definition for term 1, also wrapped in a paragraph\n" + " because of the blank line preceding it.\n\n" + "Term 2\n\n" + ": This definition has a code block, a blockquote and a list.\n\n" + " code block.\n\n" + " > block quote\n" + " > on two lines.\n\n" + " 1. first list item\n" + " 2. second list item"; final Pattern pattern = Pattern.compile(regex); 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