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

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 = "[a-z0-9!#$%&'*+\\/=?^_`\\{|\\}~-]+(?:\\.[a-z0-9!#$%&'*+\\/=?^_`\\{|\\}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\n"; final String string = "frankp@gmail.com\n" + "shannon.eee@gmail.com\n" + "franks&shannon@gmail.com\n" + "frank%ddd@gmail.com\n" + "frank@gmail$.com\n" + "frank@gmail_gmail.com\n" + "frank@gmail.research.com\n" + "joe@ggg.gg.cccc.com\n" + "joe..joe@gmail.com\n\n\n\n" + "/\n" + "https://stackoverflow.com/questions/5174171/fix-regular-expression-for-emails-to-not-allow-consecutive-periods/5174201#5174201\n\n" + "*To avoid matching two consecutive dots you can add a negative lookahead at the beginning of your regular expression:\n\n" + "/^(?!.*\\.{2})[a-z0-9etc...\n" + " ------------\n" + "It will fail to match if there are two consecutive periods anywhere in the string and it doesn't require any other modifications to your original regular expression.\n\n" + "However it seems a bad idea as your regular expression isn't correct in the first place. If you insist on using regular expressions to validate email addresses, try this:\n" + "*/\n\n" + "wilson..gmail.com\n" + "wilson.gmail.com\n" + "^(?!.*\\.{2})/[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\n\n\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