Regular Expressions 101

Save & Share

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests

Tools

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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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

Substitution

Processing...

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 = "(?<!^)((?<=[a-z])[A-Z0-9]|[A-Z](?=[a-z]))"; final String string = "Situacao\",\n" + "PES_TIPO_PESSOA\",\n" + "CedenteCnpjCpf\",\n" + "TIT_CEDENTE_ENT_CODIGO\",\n" + "CedenteNome\",\n" + "Cnae\",\n" + "SecaoCNAEDescricao\",\n" + "NotaPdd\",\n" + "SAC_TIPO_PESSOA\",\n" + "SacadoCnpjCpf\",\n" + "SacadoNome\",\n" + "IdTituloVortx\",\n" + "TipoAtivo\",\n" + "DataEmissao\",\n" + "DataAquisicao\",\n" + "DataVencimento\",\n" + "NumeroBoleto\",\n" + "NumeroTitulo\",\n" + "CampoChave\",\n" + "ValorAquisicao\",\n" + "ValorNominal\",\n" + "ValorPresente\",\n" + "PDDNota\",\n" + "PDDVencido\",\n" + "PagamentoParcial\",\n" + "Coobricacao\",\n" + "DataGeracao\",\n" + "PDDTotal\",\n" + "CampoAdicional1\",\n" + "CampoAdicional2\",\n" + "CampoAdicional3\",\n" + "CampoAdicional4\",\n" + "CampoAdicional5,\n" + "Campo22Adicional5\n" + "camelCase"; final String subst = "_\\1"; 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