Regular Expressions 101

Save & Manage Regex

  • Current Version: 2
  • Save & Share
  • Community Library

Flavor

  • PCRE2 (PHP)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java
  • .NET 7.0 (C#)
  • Rust
  • PCRE (Legacy)
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests
Sponsors
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
Processing...

Test String

Substitution
Processing...

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 = "(\\w+)=(\\w+)"; final String string = "{\n" + " \"request\": \"START_SIGNATURE\",\n" + " \"request_id\": \"9876543210\",\n" + " \"user\": \"{{user}}\",\n" + " \"password\": \"{{password}}\",\n" + " \"signature\": {\n" + " \"config_id\": 12345,\n" + " \"contract_id\": \"CompanyID1233456\",\n" + " \"level\": [\n" + " {\n" + " \"level_order\": 0,\n" + " \"required_signatories_to_complete_level\": 2,\n" + " \"signatories\": [\n" + " {\n" + " \"phone\": \"+34666666666\",\n" + " \"email\": \"signatory1@gmail.com\",\n" + " \"name\": \"Nombre1\",\n" + " \"surname\": \"Apellido1\",\n" + " \"position_id\": \"1\"\n" + " },\n" + " {\n" + " \"phone\": \"+34677777777\",\n" + " \"email\": \"signatory2@gmail.com\",\n" + " \"name\": \"Nombre2\",\n" + " \"surname\": \"Apellido2\",\n" + " \"upload_files_registered\": \"Y\",\n" + " \"position_id\": \"2\",\n" + " \"upload_files\": [\n" + " {\n" + " \"name\": \"Foto DNI\",\n" + " \"optional\": \"Y\"\n" + " }\n" + " ]\n" + " }\n" + " ]\n" + " },\n" + " {\n" + " \"level_order\": 1,\n" + " \"required_signatories_to_complete_level\": 1,\n" + " \"signatories\": [\n" + " {\n" + " \"phone\": \"+34688888888\",\n" + " \"email\": \"signatory3@gmail.com\",\n" + " \"name\": \"Nombre3\",\n" + " \"surname\": \"Apellido3\",\n" + " \"position_id\": \"3\"\n" + " }\n" + " ]\n" + " }\n" + " ],\n" + " \"file\": [\n" + " {\n" + " \"filename\": \"contract.pdf\",\n" + " \"content\": \"{{base64_file_content}}\",\n" + " \"file_group\": \"contract_files\",\n" + " \"signature_position\": [\n" + " {\n" + " \"signatory_position_id\": \"1\",\n" + " \"page\": \"all\",\n" + " \"x\": 40.0,\n" + " \"y\": 50.0,\n" + " \"height\": 20,\n" + " \"width\": 30,\n" + " \"rotation\": 0\n" + " },\n" + " {\n" + " \"signatory_position_id\": \"2\",\n" + " \"page\": \"4\",\n" + " \"x\": 80.0,\n" + " \"y\": 50.0,\n" + " \"height\": 20,\n" + " \"width\": 30,\n" + " \"rotation\": 0\n" + " },\n" + " {\n" + " \"signatory_position_id\": \"3\",\n" + " \"page\": \"last\",\n" + " \"x\": 60.0,\n" + " \"y\": 120.0\n" + " }\n" + " ]\n" + " }\n" + " ]\n" + " }\n" + "}"; final String subst = "\"$1\":\"$2\","; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE); 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