Regular Expressions 101

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  • Unit Tests (15)

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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

/
/
gxsmJ

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 = "(?:(?<=\\n)|(?<=\\A)) # Necessarily at the begining of a new line or start of string\n" + "(?<leading_space>[ ]{0,3})\n" + "(?<tag_all>\n" + " (?:\n" + " (?<div_open>\n" + " <(?<tag_name>\\S+)\n" + " (?<tag_attributes>(?&tag_attr))*\n" + " [^\\>]*\n" + " >\\n*\n" + " )\n" + " (?<content>.+?)\n" + " \\n*\n" + " (?<div_close>\n" + " (?(<leading_space>) # If leading spaces were found\n" + " (?:\n" + " (?<=\\n)\\g\\{leading_space\\} # Either there is a symmetry in leading space for open and closing tag\n" + " |\n" + " (?:(?<=\\S)[[:blank:]\\h]*) # or the closing tag is on the same line with preceding data\n" + " )\n" + " |\n" + " (?=<\\/\\g\\{tag_name\\}>) # No leading space, so we don't expect anything before the closing tag other than what has already been caught in the 'content'\n" + " )\n" + " <\\/\\g\\{tag_name\\}>\n" + " )\n" + " [[:blank:]\\h]*\\n\n" + " )\n" + " |\n" + " (?:\n" + " <!--[[:blank:]\\h\\v]*(?<html_comment>.*?)[[:blank:]\\h\\v]*-->\n" + " )\n" + " |\n" + " (?:\n" + " <\n" + " [[:blank:]\\h\\v]*\n" + " (?<tag_name>[a-zA-Z0-9][\\w\\-]+)\n" + " (?<tag_attributes>(?&tag_attr))*\n" + " [[:blank:]\\h\\v]*\n" + " \\/?\n" + " [[:blank:]\\h\\v]*\n" + " >\n" + " )\n" + ")\n" + "(?(DEFINE)\n" + " (?<tag_attr>\n" + " (?:\n" + " [[:blank:]\\h]*\n" + " [\\w\\-]+\n" + " [[:blank:]\\h]*\n" + " =\n" + " [^\\\"\\'[:blank]\\h]+\n" + " [[:blank:]\\h]*\n" + " )\n" + " |\n" + " (?:\n" + " [[:blank:]\\h]*\n" + " [\\w\\-]+\n" + " [[:blank:]\\h]*\n" + " =\n" + " [[:blank:]\\h]*\n" + " (?<quote>[\"'])\n" + " (.*?)\n" + " \\g\\{quote\\}\n" + " [[:blank:]\\h]*\n" + " )\n" + " )\n" + ")"; final String string = "<abbr title=\"`first backtick!\">SB</abbr> \n\n" + "<abbr title=\"`second backtick!\">SB</abbr>\n\n" + "<table>\n" + "<tr><td markdown=\"block\">test _emphasis_ (block)</td></tr>\n" + "</table>\n\n" + "## More complicated\n\n" + "<table>\n" + "<tr><td markdown=\"1\">\n" + "* this is _not_ a list item</td></tr>\n" + "<tr><td markdown=\"span\">\n" + "* this is _not_ a list item</td></tr>\n" + "<tr><td markdown=\"block\">\n" + "* this _is_ a list item\n" + "</td></tr>\n" + "</table>\n"; final Pattern pattern = Pattern.compile(regex, Pattern.COMMENTS | Pattern.DOTALL | 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