Email java com arquivo

import java.util.Properties;     
import javax.mail.Message;     
import javax.mail.Session;     
import javax.mail.Transport;     
import javax.mail.internet.InternetAddress;     
import javax.mail.internet.MimeMessage;     
import javax.mail.Authenticator;     
import javax.mail.PasswordAuthentication;     
import javax.swing.JOptionPane;   
  
public class Email extends javax.swing.JDialog {   
         
    private String mailSMTPServer;     
    private String mailSMTPServerPort;     
         
  
    public Email(java.awt.Frame parent, boolean modal) {   
        super(parent, modal);   
        initComponents();   
         
    }   
  
  Email() { //Para o GMAIL     
        mailSMTPServer = "smtp.gmail.com";     
        mailSMTPServerPort = "465";     
    }     
     
   Email(String mailSMTPServer, String mailSMTPServerPort) {   
        this.mailSMTPServer = mailSMTPServer;     
        this.mailSMTPServerPort = mailSMTPServerPort;     
    }     
     
       public void Email(String from, String to, String subject, String message) {                 
        Properties props = new Properties();     
     
                // quem estiver utilizando um SERVIDOR PROXY descomente essa parte e atribua as propriedades do SERVIDOR PROXY utilizado     
               
        props.put("mail.transport.protocol", "smtp");     
        props.put("mail.smtp.starttls.enable","true");     
        props.put("mail.smtp.host", mailSMTPServer);   
        props.put("mail.smtp.auth", "true");   
        props.put("mail.smtp.user", from);   
        props.put("mail.debug", "true");     
        props.put("mail.smtp.port", mailSMTPServerPort);   
        props.put("mail.smtp.socketFactory.port", mailSMTPServerPort);   
        props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");     
        props.put("mail.smtp.socketFactory.fallback", "false");     
             
        SimpleAuth auth = null;     
        auth = new SimpleAuth ("usuario login","senha login");     
             
        Session session = Session.getDefaultInstance(props, auth);     
        session.setDebug(true);   
     
        Message msg = new MimeMessage(session);     
     
        try {     
            //Setando o destinatário     
            msg.setRecipient(Message.RecipientType.TO, new InternetAddress(to));     
            msg.setFrom(new InternetAddress(from));     
            msg.setSubject(subject);     
            msg.setContent(message,"text/plain");     
     
        } catch (Exception e) {     
            System.out.println(">> Erro: Completar Mensagem");     
            e.printStackTrace();     
        }     
         
        Transport tr;     
        try {     
            tr = session.getTransport("smtp");     
  
            tr.connect(mailSMTPServer, "usuario login", "senha login");     
            msg.saveChanges();   
            tr.sendMessage(msg, msg.getAllRecipients());     
            tr.close();     
        } catch (Exception e) {     
            JOptionPane.showMessageDialog(this, "Erro ao enviar Email", "ERRO", JOptionPane.ERROR_MESSAGE);       
            System.out.println(">> Erro: Envio Mensagem");     
            e.printStackTrace();     
        }     
     
         
       }           
  
class SimpleAuth extends Authenticator {     
    public String username = null;     
    public String password = null;     
  
     
    public SimpleAuth(String user, String pwd) {     
        username = user;     
        password = pwd;     
    }     
     
    protected PasswordAuthentication getPasswordAuthentication() {     
        return new PasswordAuthentication (username,password);     
    }   
             
}   

esse codigo funciona perfeitamente para envio de mensagens queria colocar arquivo junto com a mensagem alguem teria uma ideia de como faze-lo?????????