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

/
/
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 = "^Hi.*Page (\\d+).*\\n(.*)"; final String string = "Notes and highlights for\n" + "Outlive\n" + "Attia MD, Peter\n" + "Part I\n" + "Highlight (yellow) - Chapter 1: The Long Game: From Fast Death to Slow Death > Page 10 · Location 150\n" + "In 1900 , life expectancy hovered somewhere south of age fifty , and most people were likely to die from “ fast ” causes : accidents , injuries , and infectious diseases of various kinds . Since then , slow death has supplanted fast death . The majority of people reading this book can expect to die somewhere in their seventies or eighties , give or take , and almost all from “ slow ” causes .\n" + "Highlight (yellow) - Chapter 1: The Long Game: From Fast Death to Slow Death > Page 10 · Location 154\n" + "Four Horsemen : heart disease , cancer , neurodegenerative disease , or type 2 diabetes and related metabolic dysfunction .\n" + "Highlight (yellow) - Chapter 1: The Long Game: From Fast Death to Slow Death > Page 10 · Location 155\n" + "we must understand and confront these causes of slow death .\n" + "Highlight (yellow) - Chapter 1: The Long Game: From Fast Death to Slow Death > Page 10 · Location 158\n" + "Healthspan is typically defined as the period of life when we are free from disability or disease ,\n" + "Highlight (yellow) - Chapter 1: The Long Game: From Fast Death to Slow Death > Page 14 · Location 215\n" + "It is absurd and harmful to treat this disease like a cold or a broken bone , where you either have it or you don’t ; it’s not binary .\n" + "Highlight (yellow) - Chapter 1: The Long Game: From Fast Death to Slow Death > Page 14 · Location 218\n" + "Changing that mindset must be our first step in attacking slow death . We want to delay or prevent these conditions so that we can live longer without disease , rather than lingering with disease .\n" + "Highlight (yellow) - Chapter 1: The Long Game: From Fast Death to Slow Death > Page 17 · Location 270\n" + "Exercise is by far the most potent longevity “ drug . ” No other intervention does nearly as much to prolong our lifespan and preserve our cognitive and physical function ."; final String subst = "> $2 [@attia:2023 p.$1]\\n"; 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