Two ways to validate email address #regular expression #java

 validation on the email address will be handled using two ways below :

• Regular expression 
• apache-commons Email validator.( you need to download the Jar.)

Apache Commons:

code example :

import org.apache.commons.validator.routines.EmailValidator;

boolean isValidEmail = EmailValidator.getInstance().isValid(emailAddress);

Email Regular Expression Pattern:

expression:

•      ^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*

                 @[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$;

Description:

Symbol	Meaning
^	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

Code Example:

import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class EmailValidator {
 
 private Pattern pattern;
 private Matcher matcher;
 
 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,})$";
 
 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();
 
 }
}