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
Processing...

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 = "^yahoo\\.com?(?:(?!\\.[a-z]{2}).)*(?:.com?)?$\n"; final String string = "STACK ANSWER\n" + "^yahoo\\.com?(?:(?!\\.[a-z]{2}).)*(?:.com?)?$\n\n\n" + "?: NON CAPTURING GROUP - uses this to match but doesn't include\n" + "?! NEGATIVE LOOKAHEAD - use this to look ahead to anything dot (2 chars) dot (IE .fr.) \n" + ". ANY CHARACTER\n" + "* UNLIMITED # TIMES\n" + "?: use this to match : .com? (m is optional) (expression is optional) \n" + "$ ends \n\n" + "com.fr (followed by anything)* \n" + "with optional .co OR .com \n" + ".co.kr\n\n" + "KEEP\n" + "yahoo.es\n" + "yahoo.fr\n" + "yahoo.ca\n" + "yahoo.cm\n" + "yahoo.cn\n" + "yahoo.tw\n" + "yahoo.co.jp\n" + "yahoo.co.kr\n" + "yahoo.co.uk\n" + "yahoo.com.cn\n" + "yahoo.com.hk\n" + "yahoo.com.mx\n" + "yahoo.com.tw\n\n" + "REPLACE\n" + "yah.com\n" + "yahaoo.com\n" + "yahho.com\n" + "yahhoo.com\n" + "yaho.com\n" + "yahoo\n" + "yahoo,com\n" + "yahoo.c\n" + "yahoo.co\n" + "yahoo.co,\n" + "yahoo.com\n" + "yahoo.com,\n" + "yahoo.com.\n" + "yahoo.com'\n" + "yahoo.com/haltokariev\n" + "yahoo.com>\n" + "yahoo.com21yahoo.com\n" + "yahoo.comcom\n" + "yahoo.comheatdoc1123\n" + "yahoo.comj\n" + "yahoo.comm\n" + "yahoo.comn\n" + "yahoo.comok.nicholastrami9-12-15\n" + "yahoo.comom\n" + "yahoo.comy.net\n" + "yahoo.con\n" + "yahoo.coom\n" + "yahoo.copm\n" + "yahoo.cvom\n" + "yahoo.net\n" + "yahoo.ocm\n" + "yahoo.om\n" + "yahooc.om\n" + "yahoocom\n" + "yahoogroups.com\n" + "yahool.com\n" + "yahoomail.com\n" + "yahooo.com\n"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE | Pattern.CASE_INSENSITIVE); 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