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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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

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-zA-Z]\\d{4}$"; final String string = "# The CMS, who maintain these codes, describe the format as:-\n" + "# \"HCPCS Level II codes (also known as alpha-numeric codes) consist of a single alphabetical letter followed by 4 numeric digits.\"\n" + "# (https://www.cms.gov/medicare/coding-billing/healthcare-common-procedure-system)\n" + "# NOTE: This regex will not identify HCPCS Level I codes (AKA CPT codes)\n" + "# Also, some sources say the single letter ranges only from A-V (this regex follows A-Z)\n" + "# Finally, this regex does not match procedure modifiers, which are 2 digit codes that follow a HCPCS code (with hyphen). \n" + "# (https://www.aapc.com/resources/what-are-medical-coding-modifiers)\n" + "# A separate regex has been created on regex101 supporting these modifiers\n\n" + "# Genuine codes\n" + "E8015\n" + "A6410\n" + "C5278\n" + "G2102\n" + "M1221\n" + "V2623\n" + "V2756\n" + "c5278\n" + "g2102\n" + "m1221\n" + "v2623\n" + "v2756\n" + "# Should fail\n" + "EE8015\n" + "6410\n" + "E641O\n" + "[6410\n" + "_6510\n" + "g212\n" + "C52789\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