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

@"
"
ig

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 = "(?=\\S)(?<text>(?<comment>(?<open>[#;]+)(?:[^\\S\\r\\n]*)(?<value>.+))|(?<section>(?<open>\\[)(?:\\s*)(?<value>[^\\]]*\\S+)(?:[^\\S\\r\\n]*)(?<close>\\]))|(?<entry>(?<key>[^=\\r\\n\\[\\]]*\\S)(?:[^\\S\\r\\n]*)(?<delimiter>:|=)(?:[^\\S\\r\\n]*)(?<value>[^#;\\r\\n]*))|(?<undefined>.+))(?<=\\S)|(?<linebreaker>\\r\\n|\\n)|(?<whitespace>[^\\S\\r\\n]+)"; final String string = "; Comment above the section\n" + "Key0=Value0\n" + "[Section 1]\n" + "Key=Value \n" + " [EmptySection]\n" + "Dummy text\n" + ";Commented Key=Value\n" + ";The following empty lines are ignored\n" + ";\n" + " # \n" + " \n" + " [ Section 2 ]#Comment after [section]; \n" + " Key 1 = Value 1\n" + " Key2 = Value 2 and [text in square brackets]\n" + " EmptyKey= \n" + "[];Noname section ignored\n" + " [ Section2 ] Dummy text after section\n" + " Key3 =Value 3 (symbols [;] are included) \n" + " #Key4 = Value 4 has been commented \n\n" + "Dummy text before section [ Sectionnum3 ] \n" + " Key 5 = Value 5 \n" + " Key6 =Value6 "; final Pattern pattern = Pattern.compile(regex, Pattern.CASE_INSENSITIVE); 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