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

/
/
gmi

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*(#*)\\s*(\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3})\\s+([a-zA-Z0-9\\.\\- ]+)([^#]*#?\\w*\\s*)$"; final String string = "# Copyright (c) 1993-2009 Microsoft Corp.\n" + "#\n" + "# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.\n" + "#\n" + "# This file contains the mappings of IP addresses to host names. Each\n" + "# entry should be kept on an individual line. The IP address should\n" + "# be placed in the first column followed by the corresponding host name.\n" + "# The IP address and the host name should be separated by at least one\n" + "# space.\n" + "#\n" + "# Additionally, comments (such as these) may be inserted on individual\n" + "# lines or following the machine name denoted by a '#' symbol.\n" + "#\n" + "# For example:\n" + "#\n" + "# 102.54.94.97 rhino.acme.com # source server\n" + "# 38.25.63.10 x.acme.com # x client host\n\n" + "# localhost name resolution is handled within DNS itself.\n" + "# 127.0.0.1 localhost\n" + "# ::1 localhost\n\n" + "127.0.0.1 jw smartsite.jw\n" + "127.0.0.1 dev.filepresso.com dev.filepresso.com.pl dev.filepresso.pl dev.filefly.pl\n" + "#### 89.31.66.248 sp.biatelbit.pl\n\n" + "192.168.72.51 subversion.biatel.com.pl\n" + " \n" + "# 127.0.0.1 bip.smartsite.bit-sa.pl\n" + " # 127.0.0.1 bip.augustow.wrotapodlasia.pl\n" + "127.0.0.1 rpowp.smartsite.bit-sa.pl\n" + "127.0.0.1 cms.smartsite.bit-sa.pl\n" + "127.0.0.1 cms-test.smartsite.bit-sa.pl\n\n" + "############################################################ \n" + "# \n" + "# UMWP \n" + "# \n" + "############################################################ \n\n" + "############################################################ \n" + "# ST - test - UMWP \n" + "############################################################ \n" + "#10.200.14.70 ST-sapp1 \n" + "#10.200.14.70 tv.smartsite.bit-sa.pl wp.smartsite.bit-sa.pl cms.smartsite.bit-sa.pl test.smartsite.bit-sa.pl bip.smartsite.bit-sa.pl si.smartsite.bit-sa.pl sspw.wrotapodlasia.pl \n" + "#10.200.14.70 radny.smartsite.bit-sa.pl stats.smartsite.bit-sa.pl test9.smartsite.bit-sa.pl "; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE | Pattern.CASE_INSENSITIVE); 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