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

/
/

Test String

Substitution

Processing...

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 = "(?x) # Free-Spacing\n" + "(?(DEFINE) # Define a few subroutines\n" + " (?<double>&ldquo;(?:(?!&[lr]squo;).)*&rdquo;) # full set of doubles (no quotes inside)\n" + " (?<single>&lsquo;(?:(?!&[lr]dquo;).)*&rsquo;) # full set of singles (no quotes inside)\n" + " (?<notquotes>(?:(?!&[lr][sd]quo;).)*) # chars that are not quotes\n" + ") # end DEFINE\n\n" + "^ # Start of string\n" + "( # Start group: balanced portion\n" + "(?: # Start non-capture group\n" + " (?&notquotes) # Any non-quote chars\n" + " &l(?<type>[sd])quo; # Opening quote, capture single or double type\n" + " # any full singles, doubles, not quotes or recursion\n" + " (?:(?&single)|(?&double)|(?&notquotes)|(?R))*\n" + " &r\\k<type>quo; # Closing quote of the correct type\n" + ")*+ # Repeat non-capture group\n" + ") # end balanced portion\n" + "\\K\n" + "(\n" + "(?&notquotes)\n" + "&r([sd])quo; # unmatched quote\n" + ")"; final String string = "&ldquo;Full Quote&rdquo; The Left Quote is Missing&rdquo;\n"; final String subst = "&l\\7quo;\\6"; final Pattern pattern = Pattern.compile(regex); final Matcher matcher = pattern.matcher(string); // The substituted value will be contained in the result variable final String result = matcher.replaceFirst(subst); System.out.println("Substitution result: " + result); } }

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