How to send E-mail to a Group in Java using Java Mail API ?.

Program to demonstrate how to send E-mail to a Group in Java using Java Mail API.

package com.hubberspot.email.examples;

import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import java.util.Scanner;
import javax.mail.Address;
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.AddressException;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class SendEmailToGroupDemo {

 public static void main(String[] args) {

  // Create a SendEmail object and call start 
  // method to send a mail in Java.
  SendEmailToGroupDemo sendEmailToGroup = new SendEmailToGroupDemo();
  sendEmailToGroup.start();

 }

 private void start() {

  // For establishment of email client with 
  // Google's gmail use below properties.
  // For TLS Connection use below properties
  // Create a Properties object 
  Properties props = new Properties();

  // these properties are required
  // providing smtp auth property to true
  props.put("mail.smtp.auth", "true");
  // providing tls enability
  props.put("mail.smtp.starttls.enable", "true");
  // providing the smtp host i.e gmail.com
  props.put("mail.smtp.host", "smtp.gmail.com");
  // providing smtp port as 587
  props.put("mail.smtp.port", "587");

  // For SSL Connection use below properties

  /*props.put("mail.smtp.host", "smtp.gmail.com");
   props.put("mail.smtp.socketFactory.port", "465");
   props.put("mail.smtp.socketFactory.class",
     "javax.net.ssl.SSLSocketFactory");
   props.put("mail.smtp.auth", "true");
   props.put("mail.smtp.port", "465");*/

  // Create Scanner object to take necessary 
  // values from the user.
  Scanner scanner = new Scanner(System.in);

  System.out.println("Please provide your Username for Authentication ...");
  final String Username = scanner.next();

  System.out.println("Please provide your Password for Authentication ...");
  final String Password = scanner.next();

  System.out.println("Please provide Email Address from which you want to send Email ...");
  final String fromEmailAddress = scanner.next();

  System.out.println("Please provide Email Addresses to which you want to send Email ...");
  System.out.println("If you are done type : Done or done");

  // ArrayLists to store email addresses entered by user
  ArrayList< String> emails = (ArrayList< String >) getEmails();

  System.out.println("Please provide Subject for your Email ... ");
  final String subject = scanner.next();

  System.out.println("Please provide Text Message for your Email ... ");
  final String textMessage = scanner.next();

  // Create a Session object based on the properties and 
  // Authenticator object
  Session session = Session.getDefaultInstance(props, 
    new LoginAuthenticator(Username,Password));

  try {

   // Create a Message object using the session created above
   Message message = new MimeMessage(session);

   // setting email address to Message from where message is being sent
   message.setFrom(new InternetAddress(fromEmailAddress));

   // setting the email addressess to which user wants to send message 
   message.setRecipients(Message.RecipientType.BCC, getEmailsList(emails));

   // setting the subject for the email 
   message.setSubject(subject);

   // setting the text message which user wants to send to recipients
   message.setText(textMessage);

   // Using the Transport class send() method to send message 
   Transport.send(message);

   System.out.println("\nYour Message delivered successfully ....");

  } catch (MessagingException e) {

   throw new RuntimeException(e);

  }  
 }

 // This method takes a list of email addresses and 
 // returns back an array of Address by looping the 
 // list one by one and storing it into Address[]
 private Address[] getEmailsList(ArrayList< String > emails) {

  Address[] emaiAddresses = new Address[emails.size()];

  for (int i =0;i < emails.size();i++) {
   try {
    emaiAddresses[i] = new InternetAddress(emails.get(i));
   }
   catch (AddressException e) {

    e.printStackTrace();
   }
  }
  return emaiAddresses;
 }

 // This method prompts user for email group to which he
 // wants to send message
 public List< String > getEmails() {
  ArrayList< String > emails = new ArrayList< String >();

  int counter = 1;
  String address = "";
  Scanner scanner = new Scanner(System.in);

  // looping inifinitely times as long as user enters 
  // emails one by one
  // the while loop breaks when user types done and 
  // press enter.
  while(true) {

   System.out.println("Enter E-Mail : " + counter);
   address = scanner.next();

   if(address.equalsIgnoreCase("Done")){
    break;
   }
   else {
    emails.add(address);
    counter++;
   }
  }

  return emails;
 }
}

// Creating a class for Username and Password authentication
// provided by the user.
class LoginAuthenticator extends Authenticator {
 PasswordAuthentication authentication = null;

 public LoginAuthenticator(String username, String password) {
  authentication = new PasswordAuthentication(username,password);
 }

 @Override
 protected PasswordAuthentication getPasswordAuthentication() {
  return authentication;
 }
}

Output of the program :