Java Mailing Service

hi guys...i am presently working on my mini-project in my college...and a module of it requires the use of java mailing service...i need to send a mail using SMTP protocol through my java application...i learnt that gmail can be used as a SMTP server to send mails...this is the code of my application...but when i am running this program i am getting a error stating NO CLASS FOUND javax.mail.Authenticator

Code:

import java.util.Properties;  
import javax.mail.Authenticator;
import javax.mail.Message;  
import javax.mail.MessagingException;  
import javax.mail.PasswordAuthentication;  
import javax.mail.Session;  
import javax.mail.Transport;  
import javax.mail.internet.InternetAddress;  
import javax.mail.internet.MimeMessage;  
      
   public class SendEmail
  {  
     public static void main(String args[]) throws Exception
     {
           // Set the host smtp address  
           Properties props = new Properties();  
           props.put("mail.smtp.starttls.enable", "true");  
           props.put("mail.smtp.host", "smtp.gmail.com");  
           props.put("mail.transport.protocol", "smtp");  
           props.put("mail.smtp.auth", "true");  
           Authenticator auth = new   SMTPAuthenticator("MY GMAIL ID","PASSWORD");  
           Session session = Session.getDefaultInstance(props, auth);  
           session.setDebug(false);  
            // create a message  
           Message msg = new MimeMessage(session);  
            // set the from and to address  
           InternetAddress addressFrom = new InternetAddress("praveen");  
           msg.setFrom(addressFrom);  
           InternetAddress addressTo = new InternetAddress("adroit89@yahoo.co.in");  
           msg.setRecipient(Message.RecipientType.TO, addressTo);  
           // Setting the Subject and Content Type  
           msg.setSubject("try");  
           msg.setContent("hiiii", "text/html");  
           Transport.send(msg);  
       }  
    /** 
    * SimpleAuthenticator is used to do simple authentication when the SMTP 
    * server requires it. 
    */  
         
     public static class SMTPAuthenticator extends javax.mail.Authenticator 
    {  
           private String username;  
           private String password;  
           public SMTPAuthenticator(String username, String password) 
          {  
               this.username = username;  
               this.password = password;  
           }  
           public PasswordAuthentication getPasswordAuthentication() 
          {  
               return new PasswordAuthentication(username, password);  
          }  
    }        
}