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"
"
mg

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 = "^(\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}.\\d{3}(?:Z|[+-]\\d{2}:\\d{2}))\\s*(\\w+)\\s*(\\d*)\\s*---\\s*\\[\\s*([a-zA-Z0-9\\._-]+)?\\]\\s*([^\\s]+)\\s*:\\s*([^\\n]+)$"; final String string = "2023-02-13T20:51:06.372+05:30 INFO 28357 --- [ main] com.example.demo.DemoApplication : Starting DemoApplication using Java 17.0.2 with PID 28357 (/Users/snehangshub/Documents/Experiments/demo/build/classes/java/main started by snehangshub in /Users/snehangshub/Documents/Experiments/demo)\n" + "2023-02-13T20:51:06.373+05:30 INFO 28357 --- [ main] com.example.demo.DemoApplication : No active profile set, falling back to 1 default profile: \"default\"\n" + "2023-02-13T20:51:06.715+05:30 INFO 28357 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat initialized with port(s): 8080 (http)\n" + "2023-02-13T20:51:06.721+05:30 INFO 28357 --- [ main] o.apache.catalina.core.StandardService : Starting service [Tomcat]\n" + "2023-02-13T20:51:06.721+05:30 INFO 28357 --- [ main] o.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/10.1.5]\n" + "2023-02-13T20:51:06.763+05:30 INFO 28357 --- [ main] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext\n" + "2023-02-13T20:51:06.764+05:30 INFO 28357 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 371 ms\n" + "2023-02-13T20:51:06.899+05:30 INFO 28357 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''\n" + "2023-02-13T20:51:06.903+05:30 INFO 28357 --- [ main] com.example.demo.DemoApplication : Started DemoApplication in 0.684 seconds (process running for 0.832)\n" + "2023-02-13T20:51:24.855+05:30 INFO 28357 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet'\n" + "2023-02-13T20:51:24.855+05:30 INFO 28357 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'\n" + "2023-02-13T20:51:24.858+05:30 INFO 28357 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Completed initialization in 2 ms\n" + "2023-02-13T19:09:07.379Z INFO 1 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''"; 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