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

r"
"
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]*(\\.[0-9]{0,2})?$/"; final String string = "1.22\n" + "3\n" + "999\n" + "-3\n" + "0\n" + "0.0\n" + "1.0\n" + "0.1\n" + ".01\n" + "-0.0000000000000000000000000000000001\n" + "2e3\n" + "-2e3\n" + "2e-3\n" + "-2e-3\n" + "1.0e0\n" + "0.1e1\n" + ".01e-1\n" + "-9.1e3\n" + "-9.1e-3\n" + "9E5\n" + "0e-11\n" + "0xff\n" + "0XFF\n" + "0x0\n" + "0xfe3\n" + "-0\n" + "-0.0\n" + "-0.0000000000000000000000000000000000\n" + "-.0\n" + "-.0000000000000000000000000000000000\n" + "1xff\n" + "0x\n" + "0x0fg3\n" + "0xf4.\n" + ".0xf\n" + "0xfe-3\n" + "-0xff\n" + "0.0xff\n" + "0xff.1\n" + "e89\n" + ".e3\n" + "001\n" + "-00.2\n" + "3.\n\n" + "a\n" + " -1\n" + "--1\n" + "-.1\n" + "2..3\n" + "2-\n" + "2...3\n" + "2.4.3\n" + "5-6-7\n" + ".-1"; 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