Created Registration Form With Input Field Of Email Address

i have created a registration form with an input field of email address. now i want if a new user register, it should automatically receive a confirmation mail.

i have done some coding but i am unable to define what to write on place of highlighted text.

public void sendConfEmail(){
try{
Properties props = null;
if (props == null) {
props = System.getProperties();
}
props.put("mail.smtp.host", "<server host name>");
Session session = Session.getInstance(props, null);
[code]..