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

/
/
xmg

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 = "(?(DEFINE) \n" + " (?<addr_spec> (?&local_part) @ (?&domain) ) \n" + " (?<local_part> (?&dot_atom) | (?&quoted_string) | (?&obs_local_part) ) \n" + " (?<domain> (?&dot_atom) | (?&domain_literal) | (?&obs_domain) ) \n" + " (?<domain_literal> (?&CFWS)? \\[ (?: (?&FWS)? (?&dtext) )* (?&FWS)? \\] (?&CFWS)? ) \n" + " (?<dtext> [\\x21-\\x5a] | [\\x5e-\\x7e] | (?&obs_dtext) ) \n" + " (?<quoted_pair> \\\\ (?: (?&VCHAR) | (?&WSP) ) | (?&obs_qp) ) \n" + " (?<dot_atom> (?&CFWS)? (?&dot_atom_text) (?&CFWS)? ) \n" + " (?<dot_atom_text> (?&atext) (?: \\. (?&atext) )* ) \n" + " (?<atext> [a-zA-Z0-9!#$%&'*+\\/=?^_`\\{|\\}~-]+ ) \n" + " (?<atom> (?&CFWS)? (?&atext) (?&CFWS)? ) \n" + " (?<word> (?&atom) | (?&quoted_string) ) \n" + " (?<quoted_string> (?&CFWS)? \" (?: (?&FWS)? (?&qcontent) )* (?&FWS)? \" (?&CFWS)? ) \n" + " (?<qcontent> (?&qtext) | (?&quoted_pair) ) \n" + " (?<qtext> \\x21 | [\\x23-\\x5b] | [\\x5d-\\x7e] | (?&obs_qtext) ) \n" + " # comments and whitespace \n" + " (?<FWS> (?: (?&WSP)* \\r\\n )? (?&WSP)+ | (?&obs_FWS) ) \n" + " (?<CFWS> (?: (?&FWS)? (?&comment) )+ (?&FWS)? | (?&FWS) ) \n" + " (?<comment> \\( (?: (?&FWS)? (?&ccontent) )* (?&FWS)? \\) ) \n" + " (?<ccontent> (?&ctext) | (?&quoted_pair) | (?&comment) ) \n" + " (?<ctext> [\\x21-\\x27] | [\\x2a-\\x5b] | [\\x5d-\\x7e] | (?&obs_ctext) ) \n" + " # obsolete tokens \n" + " (?<obs_domain> (?&atom) (?: \\. (?&atom) )* ) \n" + " (?<obs_local_part> (?&word) (?: \\. (?&word) )* ) \n" + " (?<obs_dtext> (?&obs_NO_WS_CTL) | (?&quoted_pair) ) \n" + " (?<obs_qp> \\\\ (?: \\x00 | (?&obs_NO_WS_CTL) | \\n | \\r ) ) \n" + " (?<obs_FWS> (?&WSP)+ (?: \\r\\n (?&WSP)+ )* ) \n" + " (?<obs_ctext> (?&obs_NO_WS_CTL) ) \n" + " (?<obs_qtext> (?&obs_NO_WS_CTL) ) \n" + " (?<obs_NO_WS_CTL> [\\x01-\\x08] | \\x0b | \\x0c | [\\x0e-\\x1f] | \\x7f ) \n" + " # character class definitions \n" + " (?<VCHAR> [\\x21-\\x7E] ) \n" + " (?<WSP> [ \\t] ) \n" + ") \n" + "^(?&addr_spec)$"; final String string = " Valid\n" + "-------\n" + "first.last@iana.org\n" + "1234567890123456789012345678901234567890123456789012345678901234@iana.org\n" + "\"first\\\"last\"@iana.org\n" + "\"first@last\"@iana.org\n" + "\"first\\\\last\"@iana.org\n" + "x@x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x2\n" + "1234567890123456789012345678901234567890123456789012345678@12345678901234567890123456789012345678901234567890123456789.12345678901234567890123456789012345678901234567890123456789.123456789012345678901234567890123456789012345678901234567890123.iana.org\n" + "first.last@[12.34.56.78]\n" + "first.last@[IPv6:::12.34.56.78]\n" + "first.last@[IPv6:::b3:b4]\n" + "first.last@[IPv6:::]\n" + "first.last@[IPv6:1111:2222:3333::4444:12.34.56.78]\n" + "\"first\\last\"@iana.org\n" + "user+mailbox@iana.org\n" + "customer/department@iana.org \n" + "customer/department=shipping@iana.org\n" + "\"Doug \\\"Ace\\\" L.\"@iana.org\n" + "+1~1+@iana.org\n" + "{_test_}@iana.org\n" + "\"[[ test ]]\"@iana.org\n" + "\"test&#13;&#10; blah\"@iana.org\n" + "(foo)cal(bar)@(baz)iamcal.com(quux)\n" + "cal(woo(yay)hoopla)@iamcal.com\n" + "cal(foo\\@bar)@iamcal.com\n" + "cal(foo\\)bar)@iamcal.com\n" + "first(Welcome to&#13;&#10; the (\"wonderful\" (!)) world&#13;&#10; of email)@iana.org\n" + "pete(his account)@silly.test(his host)\n" + "c@(Chris's host.)public.example\n\n" + " Invalid\n" + "---------\n" + "first@...........com\n" + "first.last@sub.do,com\n" + "first\\@last@iana.org\n" + "first.last\n" + ".first.last@iana.org\n" + "first.last.@iana.org\n" + "\"first\"last\"@iana.org\n" + "\"\"\"@iana.org\n" + "first\\\\@last@iana.org\n" + "Doug\\ \\\"Ace\\\"\\ Lovell@iana.org\n" + "()[]\\;:,><@iana.org\n" + "test@.\n" + "test@[123.123.123.123\n" + "test@123.123.123.123]\n\n"; final Pattern pattern = Pattern.compile(regex, Pattern.COMMENTS | 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