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 = "\\b(5[1-5][0-9]{2}[ -])([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b(5[1-5][0-9]{2})([0-9]{4}){3}\\b|\\b222[1-9][ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b222[1-9]([0-9]{4}){3}\\b|\\b22[3-9][0-9][ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b22[3-9][0-9]([0-9]{4}){3}\\b|\\b2[3-6][0-9]{2}[ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b2[3-6][0-9]{2}([0-9]{4}){3}\\b|\\b27[01][0-9][ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b27[01][0-9]([0-9]{4}){3}\\b|\\b2720[ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b2720([0-9]{4}){3}\\b"; final String string = "MasterCard:\n" + "Requirements: MasterCard numbers either start with the numbers 51 through 55 or with the numbers 2221 through 2720. All have 16 digits.\n\n" + "Pattern Parts:\n" + "Starts with numbers 51 through 55:\n" + "1) \\b(5[1-5][0-9]{2}[ -])([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b(5[1-5][0-9]{2})([0-9]{4}){3}\\b\n\n" + "Starts with numbers 2221 through 2720:\n" + "2) \\b222[1-9][ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b222[1-9]([0-9]{4}){3}\\b\n" + "3) \\b22[3-9][0-9][ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b22[3-9][0-9]([0-9]{4}){3}\\b\n" + "4) \\b2[3-6][0-9]{2}[ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b2[3-6][0-9]{2}([0-9]{4}){3}\\b\n" + "5) \\b27[01][0-9][ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b27[01][0-9]([0-9]{4}){3}\\b\n" + "6) \\b2720[ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b2720([0-9]{4}){3}\\b\n\n" + "Combining 1-6 to form one pattern:\n" + "\\b(5[1-5][0-9]{2}[ -])([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b(5[1-5][0-9]{2})([0-9]{4}){3}\\b|\\b222[1-9][ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b222[1-9]([0-9]{4}){3}\\b|\\b22[3-9][0-9][ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b22[3-9][0-9]([0-9]{4}){3}\\b|\\b2[3-6][0-9]{2}[ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b2[3-6][0-9]{2}([0-9]{4}){3}\\b|\\b27[01][0-9][ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b27[01][0-9]([0-9]{4}){3}\\b|\\b2720[ -]([0-9]{4}[ -]){2}[0-9]{4}\\b|\\b2720([0-9]{4}){3}\\b\n\n\n" + "Test Cases:\n" + "Should fire:\n" + "16 length, no space, start with 51-55 5123123412341234\n" + "16 length, dashes, start with 51-55 5123-1234-1234-1234\n" + "16 length, spaces, start with 51-55 5123 1234 1234 1234\n\n" + "16 length, no space, start with 2221-2720 2221123412341234\n" + "16 length, dashes, start with 2221-2720 2221-1234-1234-1234\n" + "16 length, spaces, start with 2221-2720 2221 1234 1234 1234\n\n" + "16 length, no space, start with 2221-2720 2241123412341234\n" + "16 length, dashes, start with 2221-2720 2241-1234-1234-1234\n" + "16 length, spaces, start with 2221-2720 2241 1234 1234 1234\n\n" + "16 length, no space, start with 2221-2720 2321123412341234\n" + "16 length, dashes, start with 2221-2720 2321-1234-1234-1234\n" + "16 length, spaces, start with 2221-2720 2321 1234 1234 1234\n\n" + "16 length, no space, start with 2221-2720 2705123412341234\n" + "16 length, dashes, start with 2221-2720 2705-1234-1234-1234\n" + "16 length, spaces, start with 2221-2720 2705 1234 1234 1234\n\n" + "16 length, no space, start with 2221-2720 2720123412341234\n" + "16 length, dashes, start with 2221-2720 2720-1234-1234-1234\n" + "16 length, spaces, start with 2221-2720 2720 1234 1234 1234\n\n" + "Should not fire:\n" + "16 length, no space, not start with 51-55 5623123412341234\n" + "16 length, dashes, not start with 51-55 5623-1234-1234-1234\n" + "16 length, spaces, not start with 51-55 5623 1234 1234 1234\n\n" + "16 length, no space, not start with 2221-2720 2220123412341234\n" + "16 length, dashes, not start with 2221-2720 2220-1234-1234-1234\n" + "16 length, spaces, not start with 2221-2720 2220 1234 1234 1234\n\n" + "Non 16 length, matches 51 pattern start 5123-1234-1234-123\n" + "Non 16 length, matches 2221 pattern start 2221-1234-1234-123\n\n" + "Malformed, matches 51 pattern start 51-2312-34-1234-1234 \n\n\n\n\n\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