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 = "(?<code1>id=\"question-summary-)(?<code2>\\d+)"; final String string = "<div class=\"question-summary\" id=\"question-summary-80407\">\n" + " <div class=\"statscontainer\">\n" + " <div class=\"statsarrow\"></div>\n" + " <div class=\"stats\">\n" + " <div class=\"vote\">\n" + " <div class=\"votes\">\n" + " <span class=\"vote-count-post \"><strong>2</strong></span>\n" + " <div class=\"viewcount\">votes</div>\n" + " </div>\n" + " </div>\n" + " <div class=\"status answered\">\n" + " <strong>1</strong>answer\n" + " </div>\n" + " </div>\n\n\n\n" + " <div class=\"views \" title=\"60 views\">\n" + " 60 views\n" + " </div>\n" + " </div>\n" + " <div class=\"summary\">\n" + " <h3><a href=\"/questions/80407/about-power-supply-of-opertional-amplifier\" class=\"question-hyperlink\">about power supply of opertional amplifier</a></h3>\n" + " <div class=\"excerpt\">\n" + " I am constructing an operational amplifier as shown in the following figure. I use a batter as supplier for the OP Amp and set it up as a non-inverting amp circuit. I saw that the output was clipped ...\n" + " </div>\n\n" + " <div class=\"tags t-op-amp\">\n" + " <a href=\"/questions/tagged/op-amp\" class=\"post-tag\" title=\"show questions tagged 'op-amp'\" rel=\"tag\">op-amp</a>\n\n" + " </div>\n" + " <div class=\"started fr\">\n\n\n" + " <div class=\"user-info \">\n" + " <div class=\"user-action-time\">\n\n\n" + " asked <span title=\"2013-08-27 21:49:14Z\" class=\"relativetime\">11 hours ago</span>\n" + " </div>\n" + " <div class=\"user-gravatar32\">\n" + " <a href=\"/users/17060/user1285419\"><div class=\"\"><img src=\"https://www.gravatar.com/avatar/08ee68b20a4eceff26f7eee99b708c08?s=32&d=identicon&r=PG\" alt=\"\" width=\"32\" height=\"32\"></div></a>\n" + " </div>\n" + " <div class=\"user-details\">\n" + " <a href=\"/users/17060/user1285419\">user1285419</a><br>\n" + " <span class=\"reputation-score\" title=\"reputation score\" dir=\"ltr\">165</span><span title=\"5 bronze badges\"><span class=\"badge3\"></span><span class=\"badgecount\">5</span></span>\n" + " </div>\n" + " </div>\n\n" + " </div>\n" + " </div>\n" + " </div>\n\n" + " <div class=\"question-summary\" id=\"question-summary-80405\">\n" + " <div class=\"statscontainer\">\n" + " <div class=\"statsarrow\"></div>\n" + " <div class=\"stats\">\n" + " <div class=\"vote\">\n" + " <div class=\"votes\">\n" + " <span class=\"vote-count-post \"><strong>4</strong></span>\n" + " <div class=\"viewcount\">votes</div>\n" + " </div>\n" + " </div>\n" + " <div class=\"status answered-accepted\">\n" + " <strong>2</strong>answers\n" + " </div>\n" + " </div>\n\n\n\n" + " <div class=\"views \" title=\"64 views\">\n" + " 64 views\n" + " </div>\n" + " </div>\n" + " <div class=\"summary\">\n" + " <h3><a href=\"/questions/80405/5v-regulator-power-dissipation\" class=\"question-hyperlink\">5V Regulator Power Dissipation</a></h3>\n" + " <div class=\"excerpt\">\n" + " I am using a 5V regulator (LP2950) from ON Semiconductor. I am using this for USB power and I'm feeding in 9V from an adapter. USB requires maximum of 500mA right? So the maximum power dissipation in ...\n" + " </div>\n\n" + " <div class=\"tags t-voltage-regulator t-surface-mount t-heatsink t-5v t-power-dissipation\">\n" + " <a href=\"/questions/tagged/voltage-regulator\" class=\"post-tag\" title=\"show questions tagged 'voltage-regulator'\" rel=\"tag\">voltage-regulator</a> <a href=\"/questions/tagged/surface-mount\" class=\"post-tag\" title=\"show questions tagged 'surface-mount'\" rel=\"tag\">surface-mount</a> <a href=\"/questions/tagged/heatsink\" class=\"post-tag\" title=\"show questions tagged 'heatsink'\" rel=\"tag\">heatsink</a> <a href=\"/questions/tagged/5v\" class=\"post-tag\" title=\"show questions tagged '5v'\" rel=\"tag\">5v</a> <a href=\"/questions/tagged/power-dissipation\" class=\"post-tag\" title=\"show questions tagged 'power-dissipation'\" rel=\"tag\">power-dissipation</a>\n\n" + " </div>\n" + " <div class=\"started fr\">\n\n\n" + " <div class=\"user-info \">\n" + " <div class=\"user-action-time\">\n\n\n" + " asked <span title=\"2013-08-27 21:39:31Z\" class=\"relativetime\">11 hours ago</span>\n" + " </div>\n" + " <div class=\"user-gravatar32\">\n" + " <a href=\"/users/10082/david-norman\"><div class=\"\"><img src=\"https://www.gravatar.com/avatar/8b073417e471077280b3fc5ff2eaf1f7?s=32&d=identicon&r=PG\" alt=\"\" width=\"32\" height=\"32\"></div></a>\n" + " </div>\n" + " <div class=\"user-details\">\n" + " <a href=\"/users/10082/david-norman\">David Norman</a><br>\n" + " <span class=\"reputation-score\" title=\"reputation score\" dir=\"ltr\">322</span><span title=\"3 silver badges\"><span class=\"badge2\"></span><span class=\"badgecount\">3</span></span><span title=\"10 bronze badges\"><span class=\"badge3\"></span><span class=\"badgecount\">10</span></span>\n" + " </div>\n" + " </div>\n\n" + " </div>\n" + " </div>\n" + " </div>"; 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