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

r"
"
xgm

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 = "^(?:\n" + " (\n" + " (?:bool|char|str)\n" + " |(?:[fiu](?:32|64))\n" + " |(?:[iu](?:8|16|128|size))\n" + " )|(\n" + " _*[A-Z][a-zA-Z0-9_]*\n" + " )\n" + ")$"; final String string = "hello world\n\n" + "str\n" + "string\n" + "String\n" + "CString\n\n" + "bool\n" + "boolean\n" + "Boolean\n\n" + "isize\n" + "usize\n" + "u128\n" + "I64\n" + "u_32\n" + "0i16\n" + "uu8\n" + "i4\n\n" + "char\n" + "Char\n" + "_char\n" + "_Char\n" + "character\n" + "_character\n\n" + "T\n" + "N\n" + "Type\n" + "NUM\n\n" + "snake_case\n" + "camelCase\n" + "PascalCase\n" + "SCREAMING_SNAKE_CASE\n\n" + "_snake_case1\n" + "_camelCase2\n" + "_PascalCase3\n" + "_SCREAMING_SNAKE_CASE4\n\n" + "1snake_case\n" + "2camelCase\n" + "3PascalCase\n" + "4SCREAMING_SNAKE_CASE"; 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