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 = "(?i)(%(25){0,}20|\\s)*(%(25){0,}24|\\$)(%(25){0,}20|\\s)*(%(25){0,}7B|\\{)(%(25){0,}20|\\s)*(%(25){0,}(6A|4A)|J)(%(25){0,}(6E|4E)|N)(%(25){0,}(64|44)|D)(%(25){0,}(69|49)|I)(%(25){0,}20|\\s)*(%(25){0,}3A|:)[\\w\\%]+(%(25){1,}3A|:)(%(25){1,}2F|\\/)[^\\n]+"; final String string = "Sample Log4j strings:\n" + "${JNDI:LDAP://\n" + "${JNDI:LDAPS://\n" + "${JNDI:RMI://\n" + "${JNDI:DNS://\n" + "${JNDI:NIS://\n" + "${JNDI:IIOP://\n" + "${JNDI:CORBA://\n" + "${JNDI:NDS://\n" + "${JNDI:HTTPS://\n" + "${JNDI:HTTP://\n" + " $ { JNDI :LDAPS://\n" + " $ { JNDI :LDAPS://\n" + "${jNDi:l%252564ap://\n\n" + "JNDI = %6A%6E%64%69\n" + "jndi = %4A%4E%44%49\n\n" + "Multi-encoding log4j strings (without spaces):\n" + "%24%7B%6A%6E%64%69%3A%2F\n" + "%2524%257B%256A%256E%2564%2569%253A\n" + "%2524%257B%256A%256E%2564%2569%253A%252F\n" + "%252524%25257B%25256A%25256E%252564%252569%25253A%25252F\n\n" + "Multi-URL Encoded string characters:\n" + "(?i)\n" + "(%(25){0,}20|\\s)*\n" + "(%(25){0,}24|$)\n" + "(%(25){0,}20|\\s)*\n" + "(%(25){0,}7B|{)\n" + "(%(25){0,}20|\\s)*\n" + "(%(25){0,}(6A|4A)|J)\n" + "(%(25){0,}(6E|4E)|N)\n" + "(%(25){0,}(64|44)|D)\n" + "(%(25){0,}(69|49)|I)\n" + "(%(25){0,}20|\\s)*\n" + "(%(25){0,}3A|:)\n" + "(%(25){0,}2F|\\/)\n" + "[\\w\\%]+\n" + "(%(25){0,}3A|:)\n" + "(%(25){0,}2F|\\/)\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