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 single character of: a, b, c or d
    [[ab][cd]]
  • 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]
  • Character class intersection
    [\w&&[^\d]]
  • 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 = "^([0-9]{1,3}\\.){3}[0-9]{1,3}(\\/([0-9]|[1-2][0-9]|3[0-2]))?$"; final String string = "192.168.0.1\n" + "192.168.0.1/\n" + "192.168.0.1/0\n" + "192.168.0.1/1\n" + "192.168.0.1/2\n" + "192.168.0.1/3\n" + "192.168.0.1/4\n" + "192.168.0.1/5\n" + "192.168.0.1/6\n" + "192.168.0.1/7\n" + "192.168.0.1/8\n" + "192.168.0.1/9\n" + "192.168.0.1/10\n" + "192.168.0.1/11\n" + "192.168.0.1/12\n" + "192.168.0.1/13\n" + "192.168.0.1/14\n" + "192.168.0.1/15\n" + "192.168.0.1/16\n" + "192.168.0.1/17\n" + "192.168.0.1/18\n" + "192.168.0.1/19\n" + "192.168.0.1/20\n" + "192.168.0.1/21\n" + "192.168.0.1/22\n" + "192.168.0.1/23\n" + "192.168.0.1/24\n" + "192.168.0.1/25\n" + "192.168.0.1/26\n" + "192.168.0.1/27\n" + "192.168.0.1/28\n" + "192.168.0.1/29\n" + "192.168.0.1/30\n" + "192.168.0.1/31\n" + "192.168.0.1/32\n" + "192.168.0.1/33\n" + "192.168.0.1/34\n" + "192.168.0.1/asd\n" + "192.168.0.1/01\n" + "192.168.0.1/00"; 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