Email address validation at client and server side

Email validation at client side(Java Script)
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function validateEmailAddress(emailAddress) { 
    var expression = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;


    return expression.test(email);
}

This function will return true if it is a valid email address otherwise false if it is invalid email address.
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Email validation at server side using Java

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import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class EmailAddressValidator{

 private Pattern pattern;
 private Matcher matcher;

 private static final String EMAIL_ADDRESS_PATTERN = "^[_A-Za-z0-9-]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";

 public EmailAddressValidator(){
 pattern = Pattern.compile(EMAIL_ADDRESS_PATTERN);
 }

 public boolean validate(final String emailId){ 
 matcher = pattern.matcher(emailId);
 return matcher.matches();

 }
 public static void main(String [] arg){
 String emailId="abc@yahoo.com";  
 EmailAddressValidator validatorObj=new EmailAddressValidator();
 System.out.println("-validate email address:"+emailId+": ---is it proper email:"+validatorObj.validate(emailId));
         
 emailId="abc @";
 System.out.println("-validate email address:"+emailId+": ---is it proper email:"+validatorObj.validate(emailId));
 
 }
}
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At server side you can use this class as a utility class and use wherever you want.