GMailSender class for the Java Mail API on Android tutorial

GMailSender.java

public class GMailSender extends javax.mail.Authenticator {
  private String mailhost = "smtp.gmail.com";
  private String user;
  private String password;
  private Session session;
 
  static {
    Security.addProvider(new JSSEProvider());
  }
 
  public GMailSender(String user, String password) {
    this.user = user;
    this.password = password;
 
    Properties props = new Properties();
    props.setProperty("mail.transport.protocol", "smtp");
    props.setProperty("mail.host", mailhost);
    props.put("mail.smtp.auth", "true");
    props.put("mail.smtp.port", "465");
    props.put("mail.smtp.socketFactory.port", "465");
    props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");
    props.put("mail.smtp.socketFactory.fallback", "false");
    props.setProperty("mail.smtp.quitwait", "false");
 
    session = Session.getDefaultInstance(props, this);
  }
 
  protected PasswordAuthentication getPasswordAuthentication() {
    return new PasswordAuthentication(user, password);
  }
 
  public synchronized void sendMail(String subject, String body,
    String sender, String recipients) throws Exception {
    MimeMessage message = new MimeMessage(session);
    DataHandler handler = new DataHandler(new ByteArrayDataSource(body.getBytes(), "text/plain"));
    message.setSender(new InternetAddress(sender));
    message.setSubject(subject);
    message.setDataHandler(handler);
 
    if (recipients.indexOf(',') > 0)
      message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(recipients));
    else
      message.setRecipient(Message.RecipientType.TO, new InternetAddress(recipients));
 
    Transport.send(message);
  }
}