Java Regex Tester

The Java Regex Tester by Qodex helps developers write, test, and debug regular expressions in real time using Java’s java.util.regex package. It supports instant pattern testing for emails, passwords, phone numbers, dates, credit cards, and more.

You can view live match results, capture groups, and syntax feedback instantly—making it easy to refine your regex before using it in Java code.

How to Use:

1. Enter your regular expression.

2. Provide a test string.

3. Instantly see highlighted matches and capture groups.

Need test inputs? Try our:

• Email Generator

• UUID Generator

• Phone Number Generator

• Password Generator

Java Regex Syntax Essentials

Metacharacters:

. Match any character (except newline)

^ Match start of string

$ Match end of string

| Logical OR operator (cat|dog)

Character Classes:

[abc] Match a, b, or c

[^abc] Match anything except a, b, or c

[a-zA-Z] Match any letter

\d Digit (0–9)

\D Non-digit

\w Word character

\W Non-word

\s Whitespace

\S Non-whitespace

Quantifiers

* Zero or more

+ One or more

? Zero or one

{n} Exactly n

{n,} At least n

{n,m} Between n and m

Groups & Captures

(abc) Capturing group

(?:abc) Non-capturing

(?i) Case-insensitive

\1\2 Backreferences

\b Word boundary

\B Non-word boundary

Assertions

(?=…) Positive lookahead

(?!…) Negative lookahead

(?<=…) Positive lookbehind

(?<!…) Negative lookbehind

Greedy vs Lazy

*? Lazy zero or more

+? Lazy one or more

?? Lazy zero or one

Unicode Matching

\p{L} Any letter

\p{N} Any number

\P{L} Any non-letter

Useful in multilingual or global apps.

Common Java Regex Examples

1. Email Validation

Use with Email Regex Java Validator

Pattern.compile("^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$");

2. Strong Password Check

Test using Password Regex Java Validator.

"(?=.*[a-z])(?=.*[A-Z])(?=.*\\d)(?=.*[@$!%*?&])[A-Za-z\\d@$!%*?&]{8,}"

3. Phone Number Formats

Covers (123) 456-7890, 1234567890, 123-456-7890

Pattern.compile("^(\\d{10}|\\(\\d{3}\\)[\\s.-]?\\d{3}[\\s.-]\\d{4}|\\d{3}[\\s.-]\\d{3}[\\s.-]\\d{4})$")

4. Credit Card Pattern Matching

Use Credit Card Regex Java Validator + Luhn check for full validation.

Pattern.compile("^4[0-9]{12}(?:[0-9]{3})?$") // VISA

5. Date Formats (ISO / US)

Regex checks format only—use Java date libraries for real validation.

"\\d{4}-\\d{2}-\\d{2}" // ISO  
"\\d{2}/\\d{2}/\\d{4}" // US MM/DD/YYYY

6. Extract Filename from Windows Path

Pattern.compile("[^\\\\]+$");

7. Validate IPv4

"^(?:(?:25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)\\.){3}(?:25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)$"

8. Validate 24-hour Time Format (HH:MM)

"^([01]\\d|2[0-3]):[0-5]\\d$"

9. Validate Hex Colors

Matches 3 or 6-digit codes, with or without #.

"^#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3})$"

10. SIN / SSN / ZIP Code Patterns

Check formatting only. Use:

• ^\d{3}-\d{2}-\d{4}$ for SSN

• ^\d{5}(-\d{4})?$ for ZIP +4

Important Tips

• Always escape regex characters twice in Java (e.g., \\. to match a literal dot).

• Prefer non-capturing groups unless you need references.

• Avoid regex for parsing structured formats like JSON, HTML, or XML—use parsers.

• Use Pattern.compile() once to reuse compiled patterns for better performance.

• Use [\s\S] instead of . for multiline matching when DOTALL mode is needed.

Bonus: Example Code Snippet

import java.util.regex.*;

public class RegexExample {
    public static void main(String[] args) {
        String email = "test@example.com";
        Pattern pattern = Pattern.compile("^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$");
        Matcher matcher = pattern.matcher(email);
        System.out.println("Email valid: " + matcher.matches());
    }
}

Test More Regex Patterns in Java:

• Email Regex Java Validator

• Password Regex Java Validator

• Phone Number Regex Java Validator

• Credit Card Regex Java Validator

• UUID Regex Java Validator

• Date Regex Java Validator

Want to test in a different language? Try our:

• JavaScript Regex Tester

• Go Regex Tester

• Python Regex Tester