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

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+_[A-Za-z]+\\._)"; final String string = "was from an authentic copy, and a careful comparison of the text with\n" + "the earlier one shows that in the meantime the play \"underwent revision,\n" + "received some slight augmentation, and in some few places must have been\n" + "entirely rewritten.\" A marked instance of this rewriting--the only one\n" + "of considerable length--is in ii. 6. 6-37, where the first quarto reads\n" + "thus (spelling and pointing being modernized):--\n\n" + " _Jul._ Romeo.\n\n" + " _Rom._ My Juliet, welcome. As do waking eyes\n" + " Closed in Night's mists attend the frolick Day,\n" + " So Romeo hath expected Juliet,\n" + " And thou art come.\n\n" + " _Jul._ I am, if I be Day,\n" + " Come to my Sun: shine forth and make me fair.\n\n" + " _Rom._ All beauteous fairness dwelleth in thine eyes.\n\n" + " _Jul._ Romeo, from thine all brightness doth arise.\n\n" + " _Fri._ Come, wantons, come, the stealing hours do pass,\n" + " Defer embracements till some fitter time.\n" + " Part for a while, you shall not be alone\n" + " Till holy Church have joined ye both in one.\n\n" + " _Rom._ Lead, holy Father, all delay seems long.\n\n" + " _Jul._ Make haste, make haste, this lingering doth us wrong.\n\n" + "For convenient comparison I quote the later text here:--\n\n" + " _Juliet._ Good even to my ghostly confessor.\n\n" + " _Friar Laurence._ Romeo shall thank thee, daughter, for us both.\n\n" + " _Juliet._ As much to him, else is his thanks too much.\n\n" + " _Romeo._ Ah, Juliet, if the measure of thy joy\n" + " Be heap'd like mine and that thy skill be more\n" + " To blazon it, then sweeten with thy breath\n" + " This neighbour air, and let rich music's tongue\n" + " Unfold the imagin'd happiness that both\n" + " Receive in either by this dear encounter.\n\n" + " _Juliet._ Conceit, more rich in matter than in words,\n" + " Brags of his substance, not of ornament.\n" + " They are but beggars that can count their worth;\n" + " But my true love is grown to such excess\n" + " I cannot sum up half my sum of wealth.\n\n" + " _Friar Laurence._ Come, come with me, and we will make short work;\n" + " For, by your leaves, you shall not stay alone\n" + " Till holy church incorporate two in one.\n\n" + "The \"omission, mutilation, or botching\" by which some German editors\n" + "would explain all differences between the earlier and later texts will\n" + "not suffice to account for such divergence as this. \"The two dialogues\n" + "do not differ merely in expressiveness and effect; they embody different\n" + "conceptions of the characters;\" and yet we cannot doubt that both were\n" + "written by Shakespeare.\n"; 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