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
No Match

/
/
g

Test String

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 = "\\s?\\battr\\s*=\\s*\"\\s*\"|\\s?\\battr\\b\\s*=(?![^=<>]*\")(?!\\s*=)|(?<!\\<)\\s*\\battr\\b(?![^=<>]*\")(?!\\s*=)"; final String string = "Nowy test:\n" + "<attr attr src=\"/test-image_1.jpg\" attr = \" \" asd=\" q\" attr=\"test-image_1.jpg\" attr qwe=\"as-d q-q\" x=\"attr asd\" >\n\n" + "Poprzedni test:\n" + "<img src=\"/test-image_1.jpg\" attr=\"test-image_1\" qwe=\"asd\" attr=>\n" + "<img src=\"/test-image_1.jpg\" attr= \"test-image_1\" qwe=\"asd\" attr=\"\">\n" + "<img src=\"/test-image_1.jpg\" attr= \"test-image_1\" qwe=\"asd\" attr=\" \">\n" + "<img attr=\"a attr b\" src=\"/test-imagalte_1.jpg\" attr qwe=\"asd\" />\n" + "<img src=\"/test- alt image_1.jpg\" attr=\"test-image_1\" attr= \"\" qwe=\"asd\" >\n" + "<img src=\"/test-image_1.jpg\" attr = \" \" asd=\" q\" attr=\"test-image_1\" attr qwe=\"asd\" >\n\n\n" + "<img src=\"/test-image_1.jpg\" attr= \"test-image_1\" qwe=\"asd\" attr=\" d \" attr = \" d \" attr= \" d \">\n" + "<img attr=\"test-image_1\" qwe=\"asd\" attr >\n" + "<img attr=\"test-image_1\" qwe=\"asd\" battr >\n" + "<img attr=\"test-image_1\" qwe=\"asd\" attrh >\n\n\n" + "<img attr=\"test-image_1\" qwe=\"asd\" attr >\n" + "<img attr=\"test-image_1\" qwe=\"asd\" attr =>\n" + "<img attr=\"test-image_1\" qwe=\"asd\" attr=>\n" + "<img attr=\"test-image_1\" qwe=\"asd\" battr = \"\" >\n" + "<img attr=\"test-image_1\" qwe=\"asd\" attrh= \" \" >\n"; final Pattern pattern = Pattern.compile(regex); 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