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 = "([\\w]+)[ \\t]+=[ \\t](Solver[ \\t]*\\(([\\d.]+)[ \\t]*,[ \\t]*([\\d.]+)[ \\t]*,[ \\t]*([\\d.]+)[ \\t]*\\))\\n\\r?demo[ \\t]*\\(\\1\\.b[ \\t]*,[ \\t]*\\1\\.a[ \\t]*,[ \\t]*\\1\\.c[ \\t]*\\)"; final String string = "import math\n\n" + "class Solver(object):\n" + " def __init__(self, a, b, c):\n" + " self.a = a\n" + " self.b = b\n" + " self.c = c\n\n\n" + "def demo(b, a, c):\n" + " d = b ** 2 - 4 * a * c\n" + " if d >= 0:\n" + " disc = math.sqrt(d)\n" + " root1 = (- b + disc) / (2 * a)\n" + " root2 = (- b - disc) / (2 * a)\n" + " print(root1, root2)\n" + " return root1, root2\n" + " else:\n" + " raise Exception\n\n\n" + "s = Solver(2, 123, 0.025)\n" + "demo(s.b, s.a, s.c)"; final String subst = "$2\\.demo()"; 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