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

r"
"
gsx

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<content>.*?) # Content up to next tag\n" + "(?P<markup> # Entire tag\n" + " <!\\[CDATA\\[(?P<cdata>.+?)]]>| # <![CDATA[ ... ]]>\n" + " <!--(?P<comment>.+?)-->| # <!-- Comment -->\n" + " </\\s*(?P<close_tag>\\w+)\\s*>| # </tag>\n" + " <(?P<tag>\\w+) # <tag ...\n" + " (?P<attributes>\n" + " (?P<attribute>\\s+\n" + "# <snip>: Use this part to get the attributes out of 'attributes' group.\n" + " (?P<attribute_name>\\w+)\n" + " (?:\\s*=\\s*\n" + " (?P<attribute_value>\n" + " [\\w:/.\\-]+| # Unquoted\n" + " (?=(?P<_v> # Quoted\n" + " (?P<_q>['\\\"]).*?(?<!\\\\)(?P=_q)))\n" + " (?P=_v)\n" + " ))?\n" + "# </snip>\n" + " )*\n" + " )\\s*\n" + " (?P<is_self_closing>/?) # Self-closing indicator\n" + " >) # End of tag\n"; final String string = "In this case, $url will indeed contain http://example.com/whatever.jpg. But what happens when you start getting HTML like this:\n\n" + "<img src='http://example.com/whatever.jpg'>\n" + "or\n\n" + "<img src=http://example.com/whatever.jpg>\n" + "or\n\n" + "<img border=0 src=\"http://example.com/whatever.jpg\">\n" + "or\n\n" + "<img border src=\"http://example.com/whatever.jpg\">\n" + "or\n\n" + "<img\n" + " src=\"http://example.com/whatever.jpg\">\n" + "or you start getting false positives from\n\n" + "<!-- // commented out\n" + "<img src=\"http://example.com/outdated.png\">\n" + "-->\n\n" + "<script><![CDATA[ This is <b>not</b> parsed ]]></script>\n\n" + "<asd ASD=asd>\n\n" + "<!-- // commented out <img src=\"http://example.com/outdated.png\"> -->\n\n" + "No quotes:\n" + "<iframe src=test.html target=xyz></ iframe >\n" + "Self-closing tag:\n" + "<a href=test.html target=xyz/>\n" + "Self closing tag with a space before closure:\n" + "<a href=test.html target=xyz />\n" + "Double quotes:\n" + "<a href=\"test.html\" target=\"xyz\">\n" + "Single quotes:\n" + "<a href='test.html' target='xyz'>\n" + "Escaping double quotes:\n" + "<a href=\"test.html?val=1\" title=\"\\\"No rules exist\\\" Andre Breton's quote\">\n" + "Escaping single quotes (also with spaces between equals signs):\n" + "<a href = \"test.html?val=1\" title = 'Charlie\\'s Angels'>\n" + "Tag without closure (ignored):\n" + "<a href = \"test.html?val=1\" title='Charlie\\'s Angels'\n" + "Tag without opening (ignored):\n" + "a href = \"test.html?val=1\" title=\"Charlie\\\"s Angels\">\n\n"; final Pattern pattern = Pattern.compile(regex, Pattern.DOTALL | Pattern.COMMENTS); 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