Regular Expressions 101

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  • Unit Tests (6)

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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"
"
g

Test String

Substitution

Processing...

Code Generator

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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]*?)\"([^\";\\n]+?)\"([^\";\\n]*?)\"(\\n|;|$)"; final String string = "A stable and simple RegEx, which escapes double-quotes (\") in a CSV file.\n\n" + "## Tests ##\n" + "\"Great thing?!*\";\"I love RegEx!\";\"And especially \"regex101.com\"!\";\"Just amazing...\"\n" + "\"Something090324*?!*\";\"Somethi\"ng090\"324*?!*\";\"Something090324*?!*\";\"Something090324*?!*\"\n" + "Ignore\"THIS\"ItIsNotARealQuote?!*;\"This\"is\"real!\";HereIsNoQuoteSymbolAtAll;This\"IsOnlyOneQuoteSymbol\n\n" + "CSV: Escape double-quotes (\") in quoted \n\n" + "## Issues ##\n" + "- Does not support embedded line breaks, but you can easily modify it to support them. Note that they are currently forbitten to be more stable.\n" + "- Does only allow \" for quoting. (Replace it in the whole RegEx to change this)\n" + "- Only works with ; as a separator. (Replace it in the whole RegEx to change this)\n" + "- Does not allow separator character inside of quotes string. Look at the following example:\n" + "\"Example \"string\"\";\"works\"\n" + "\"Example \"string\";\";\"fails\"\n" + "- Get's problems when the issue happens \"too often\", which means it shows up in cells which are directly side-by-side. You may work around this issue by running it multiple times:\n" + "\"run 1 time \";\"a string with a \"small\" issue\";\"and \"another\" one\"\n" + "\"run 2 times\";\"a string with a \"\"small\"\" issue\";\"and \"another\" one\"\n" + "- It only works with quoted strings (no single \" are escaped; only double ones)\n\n" + "## Changelog ##\n" + "v1.0 - 2016-01-25\n" + "- released\n\n" + "Author: rugk <rugk@posteo.de>"; final String subst = "\\1\"\\2\"\"\\3\"\"\\4\"\\5"; final Pattern pattern = Pattern.compile(regex); final Matcher matcher = pattern.matcher(string); // The substituted value will be contained in the result variable final String result = matcher.replaceAll(subst); System.out.println("Substitution result: " + result); } }

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