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

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 = "^(?P<indentation>(?P<sp_or_tab>[ \\t])*+)(?P<stmt>(?P<non_str_lit>(?:(?!\\#)[^\\\"'\\r\\n])*?)(?:(?P<str_lit>(?P<begin_quote>(?P<single_quote>')|\\\")(?:(?(single_quote)\\\"|')|\\\\[\\\"']|\\\\[^\\r\\n ]|[^\\\"'\\\\\\r\\n])*?(?P=begin_quote))(?&non_str_lit))*?)(?P<whitespace>(?&sp_or_tab)*+)(?P<comment>(?:\\#)[^\\r\\n]*+)?(?P<line_ending>\\r|\\n|\\r\\n)?$"; final String string = "print(\"Hello, world!\") # this is a comment.\n" + "print(\"The quick \\\\brown\\\\\\ndog\\rfox\\tjumps\\t over #the# /lazy/ \\\"dog\\\"###\") # and here's where the real comment starts\n" + " print(\"you can use Alt+0009 to enter a tab character!\")\n" + "# The above line had no comments, so the <comment> group didn't participate in the match.\n" + " print(\"indented code\") # with comment\n" + " print(\"never indent code like this, but it still matches anyway\")# comment lacking preceding whitespace >:)\n" + " print(\"space indented code\")\n" + "print(\"Missing end quote\n" + "print(\"unescaped \\\")\n" + "print(\"implicitly\" \" joined## \" \"string \" \"lit#erals\") # a line can contain multiple string literals\n" + "print(\"the quick \" # line 1\n" + " \"brown fox \" # line 2\n" + " \"jumps over \" # line 3\n" + " \"the lazy dog\") # line 4\n\n" + " print(\"The quick brown\", animal, \"jumps over the\", adjective, animal2, sep=\" \") \"\n" + "print('Robert'); DROP TABLE `Students`; -- ')"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE); final Matcher matcher = pattern.matcher(string); while (matcher.find()) { System.out.println("Full match: " + matcher.group(0)); for (int i = 1; i <= matcher.groupCount(); i++) { System.out.println("Group " + i + ": " + matcher.group(i)); } } } }

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