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

/
/
gm

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 = "(?:\\\"(?:(?<=\\\"(?=[^\\n]))[^\\n]+?(?=(?<!\\\\))(?=\\\"))?\\\")|(\\B'(?:(?<='(?=[^\\n]))[^\\n]+?(?=(?<!\\\\))(?='))?')"; final String string = "\n" + "1. Valid double-quoted strings:\n" + " - \"Hello\"\n" + " - \"This is a test\"\n" + " - \"123\"\n" + " - \"Special characters: @#$%^&*()_+\"\n" + " - \"Escape sequence: \\n\"\n\n" + "2. Valid double-quoted strings with additional characters or variables:\n" + " - \" test aaaaa \\\" \" + asdf\n" + " - \" test \" + ( \"aaaaa\" ) + gdf\n" + " - \" test \\\" \" + `\" aaaa \" + dfg\n" + " - \" test ' aaaaa \\\" \" + dfg\n" + " - \"\"\n\n" + "3. Valid double-quoted strings with special characters:\n" + " - \"sas''as\\\"a1\\'2 ! -_?:sa\"\n" + " - \"''\"\n" + " - \"\\abnb\\ajhgf\\crt098& \\\"'\"\n\n" + "4. Invalid double-quoted strings:\n" + " - \" test \" + ( \"aaaaa\" ) \\\" saf\n" + " - \"\\\\ + \\* test \" \\$ \\. dsdfs\n" + " - (\\\" test \\\" \" + \" aaaa \" sfgd\n" + " - ' test ' + aas ( \"aaaaa\" ) + '\\ sd\n" + " - '\\\\ + \\* test ' \\$ \\. trace\n" + " - (' test ' as ' + ' aaaa '\n" + " - '\"\"'\n" + " - '\"sas'\n" + " - 'ads'\n" + " - 'asdasd\\\"asdsa'\n" + " - \"klkl\"klkl\n" + " - \"asa\\'sasa\\\\\"\n" + " - \\'\\\\\\'\n" + " - \"hhhh\"klkl\"\n" + " - 'jkjkjk'klklk'\n" + " - '\\\"\\\\\\\"'\n" + " - ''\n" + " - '\\\"asa\\'sasa\\\\\\\"'\n" + " - \"sasasasa\\\\\\\\\\\\\"\n\n\n\n" + "1. Valid single-quoted strings:\n" + " - 'Hello'\n" + " - 'This is a test'\n" + " - '123'\n" + " - 'Special characters: @#$%^&*()_+'\n" + " - 'Escape sequence: \\n'\n\n" + "2. Valid single-quoted strings with additional characters or variables:\n" + " - ' test aaaaa \\' ' + asdf\n" + " - ' test ' + ( 'aaaaa' ) + gdf\n" + " - ' test \\' ' + ' aaaa' + dfg\n" + " - ' test \" aaaaa \\' ' + dfg\n" + " - ''\n\n" + "3. Valid single-quoted strings with special characters:\n" + " - 'sas\"\"as\\'a1\\\"2 ! -_?:sa'\n" + " - '\"\"'\n" + " - '\\abnb\\ajhgf\\crt098& \\'\"\"'\n\n" + "4. Invalid single-quoted strings:\n" + " - ' test ' + ( 'aaaaa' ) \\' saf\n" + " - '\\\\ + \\* test ' \\$ \\. dsdfs\n" + " - (\\' test \\' + ' aaaa ' sfgd\n" + " - \" test \\\" \" + \" aaaa \" sfgd\n" + " - ' test ' + aas ( 'aaaaa' ) + '\\ sd\n" + " - '\\\\ + \\* test ' \\$ \\. trace\n" + " - (' test ' as ' + ' aaaa '\n" + " - \"''\"\n" + " - 'sas\"\n" + " - \"ads'\n" + " - 'asdasd\\'asdsa'\n" + " - \"klkl\"klkl\n" + " - \"asa\\'sasa\\\\\"\n" + " - \\'\\\\\\'\n" + " - 'hhhh\"klkl\\'\\\n" + " - \\'jkjkjk\"klklk'\n" + " - \"\\'\\\\\\'\"\n" + " - ''\n" + " - '\\\"asa\\'sasa\\\\\\\"'\n" + " - 'sasasasa\\\\\\\\\\\\'\n"; 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