Email Regular Expression Pattern
Description
Whole combination is means, email address must start with “_A-Za-z0-9-” , optional follow by “.[_A-Za-z0-9-]“, and end with a “@” symbol. The email’s domain name must start with “A-Za-z0-9″, follow by first level Tld (.com, .net) “.[A-Za-z0-9]” and optional follow by a second level Tld (.com.au, .com.my) “\\.[A-Za-z]{2,}”, where second level Tld must start with a dot “.” and length must equal or more than 2 characters.
/*
* restTestApp - EmailValidator.java, Dec 21, 2011 11:44:50 PM
*
*/
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* The Class EmailValidator.
* @author Rajakrishna V. Reddy
*/
public class EmailValidator
{
/** The pattern. */
private Pattern pattern;
/** The matcher. */
private Matcher matcher;
/** The Constant EMAIL_PATTERN. */
private static final String EMAIL_PATTERN = "^[_A-Za-z0-9-]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";
/**
* Instantiates a new email validator.
*/
public EmailValidator()
{
pattern = Pattern.compile(EMAIL_PATTERN);
}
/**
* Validate hex with regular expression.
*
* @param hex
* hex for validation
* @return true valid hex, false invalid hex
*/
public boolean validate(final String hex)
{
matcher = pattern.matcher(hex);
return matcher.matches();
}
public static void main(String[] args)
{
final String email = "yahoo.com@yahoo.com";
final EmailValidator emailValidator = new EmailValidator();
System.out.println("Is a Valid Email: "+emailValidator.validate(email));
}
}
2. “mkyong111@mkyong.com”, “mkyong-100@mkyong.net”,”mkyong.100@mkyong.com.au”
3. “mkyong@1.com”, “mkyong@gmail.com.com”
2. “mkyong@.com.my” – tld can not start with dot “.”
3. “mkyong123@gmail.a” – “.a” is not a valid tld, last tld must contains at least two characters
4. “mkyong123@.com” – tld can not start with dot “.”
5. “mkyong123@.com.com” – tld can not start with dot “.”
6. “.mkyong@mkyong.com” – email’s first character can not start with dot “.”
7. “mkyong()*@gmail.com” – email’s is only allow character, digit, underscore and dash
8. “mkyong@%*.com” – email’s tld is only allow character and digit
9. “mkyong..2002@gmail.com” – double dots “.” are not allow
10. “mkyong.@gmail.com” – email’s last character can not end with dot “.”
11. “mkyong@mkyong@gmail.com” – double “@” is not allow
12. “mkyong@gmail.com.1a” -email’s tld which has two characters can not contains digit
^[_A-Za-z0-9-]+(\\.[_A-Za-z0-9-]+)*@ [A-Za-z0-9]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$
Description
^ #start of the line [_A-Za-z0-9-]+ # must start with string in the bracket [ ], must contains one or more (+) ( # start of group #1 \\.[_A-Za-z0-9-]+ # follow by a dot "." and string in the bracket [ ], must contains one or more (+) )* # end of group #1, this group is optional (*) @ # must contains a "@" symbol [A-Za-z0-9]+ # follow by string in the bracket [ ], must contains one or more (+) ( # start of group #2 - first level TLD checking \\.[A-Za-z0-9]+ # follow by a dot "." and string in the bracket [ ], must contains one or more (+) )* # end of group #2, this group is optional (*) ( # start of group #3 - second level TLD checking \\.[A-Za-z]{2,} # follow by a dot "." and string in the bracket [ ], with minimum length of 2 ) # end of group #3 $ #end of the line
Whole combination is means, email address must start with “_A-Za-z0-9-” , optional follow by “.[_A-Za-z0-9-]“, and end with a “@” symbol. The email’s domain name must start with “A-Za-z0-9″, follow by first level Tld (.com, .net) “.[A-Za-z0-9]” and optional follow by a second level Tld (.com.au, .com.my) “\\.[A-Za-z]{2,}”, where second level Tld must start with a dot “.” and length must equal or more than 2 characters.
Java Regular Expression Example
Here’s a Java example to show the use of regex to validate an email address./*
* restTestApp - EmailValidator.java, Dec 21, 2011 11:44:50 PM
*
*/
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/**
* The Class EmailValidator.
* @author Rajakrishna V. Reddy
*/
public class EmailValidator
{
/** The pattern. */
private Pattern pattern;
/** The matcher. */
private Matcher matcher;
/** The Constant EMAIL_PATTERN. */
private static final String EMAIL_PATTERN = "^[_A-Za-z0-9-]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";
/**
* Instantiates a new email validator.
*/
public EmailValidator()
{
pattern = Pattern.compile(EMAIL_PATTERN);
}
/**
* Validate hex with regular expression.
*
* @param hex
* hex for validation
* @return true valid hex, false invalid hex
*/
public boolean validate(final String hex)
{
matcher = pattern.matcher(hex);
return matcher.matches();
}
public static void main(String[] args)
{
final String email = "yahoo.com@yahoo.com";
final EmailValidator emailValidator = new EmailValidator();
System.out.println("Is a Valid Email: "+emailValidator.validate(email));
}
}
Emails that match:
1. “mkyong@yahoo.com”, “mkyong-100@yahoo.com”,”mkyong.100@yahoo.com”2. “mkyong111@mkyong.com”, “mkyong-100@mkyong.net”,”mkyong.100@mkyong.com.au”
3. “mkyong@1.com”, “mkyong@gmail.com.com”
Emails that doesn’t match:
1. “mkyong” – must contains “@” symbol2. “mkyong@.com.my” – tld can not start with dot “.”
3. “mkyong123@gmail.a” – “.a” is not a valid tld, last tld must contains at least two characters
4. “mkyong123@.com” – tld can not start with dot “.”
5. “mkyong123@.com.com” – tld can not start with dot “.”
6. “.mkyong@mkyong.com” – email’s first character can not start with dot “.”
7. “mkyong()*@gmail.com” – email’s is only allow character, digit, underscore and dash
8. “mkyong@%*.com” – email’s tld is only allow character and digit
9. “mkyong..2002@gmail.com” – double dots “.” are not allow
10. “mkyong.@gmail.com” – email’s last character can not end with dot “.”
11. “mkyong@mkyong@gmail.com” – double “@” is not allow
12. “mkyong@gmail.com.1a” -email’s tld which has two characters can not contains digit
Unit Test – Result
Here’s the unit test result.Email is valid : mkyong@yahoo.com , true
Email is valid : mkyong-100@yahoo.com , true
Email is valid : mkyong.100@yahoo.com , true
Email is valid : mkyong111@mkyong.com , true
Email is valid : mkyong-100@mkyong.net , true
Email is valid : mkyong.100@mkyong.com.au , true
Email is valid : mkyong@1.com , true
Email is valid : mkyong@gmail.com.com , true
Email is valid : mkyong , false
Email is valid : mkyong@.com.my , false
Email is valid : mkyong123@gmail.a , false
Email is valid : mkyong123@.com , false
Email is valid : mkyong123@.com.com , false
Email is valid : .mkyong@mkyong.com , false
Email is valid : mkyong()*@gmail.com , false
Email is valid : mkyong@%*.com , false
Email is valid : mkyong..2002@gmail.com , false
Email is valid : mkyong.@gmail.com , false
Email is valid : mkyong@mkyong@gmail.com , false
Email is valid : mkyong@gmail.com.1a , false
PASSED: ValidEmailTest([Ljava.lang.String;@1a626f)
PASSED: InValidEmailTest([Ljava.lang.String;@1975b59)
===============================================
com.mkyong.regex.EmailValidatorTest
Tests run: 2, Failures: 0, Skips: 0
===============================================
===============================================
mkyong
Total tests run: 2, Failures: 0, Skips: 0
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