Apex Coding on Sending Email................

public class EmailNotify
{
 public static void SendEmail(Contact[] con)
 {
   Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage();
  for (Contact c:con)
  {
    if (DAY(TODAY()==15)
    {
        Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage();
        email.setSubject('Subject');      
        email.setReplyTo('whoever');
        email.setSaveAsActivity(false);
        email.setPlainTextBody('Text body');      
        String[] toAddresses = new String[] {'sampath@thylaksoft.com'};    
        email.setToAddresses(toAddresses);          
        Messaging.SendEmailResult[] sendResult;
        //send the eMail
        sendResult = Messaging.sendEmail(new Messaging.SingleEmailMessage[] { email });
    }
  }
 }
}


public void SendEmail()
{
Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
mail.setTargetObjectId(con.Id);
mail.setTemplateId('00X90000000QHUD');
Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });
}
}



public class EmailNotify
{
 public static void SendEmail(Opportunity[] opp)
 {
  for (Opportunity o:opp)
  {
    // select id from opportunity where CreatedDate < THIS_WEEK
    Date obj = Date.today();
    Integer n = FLOOR(TODAY());
    if (n = 10)
    {
        Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage();
        email.setSubject('Subject');      
        email.setReplyTo('whoever');
        email.setSaveAsActivity(false);
        email.setPlainTextBody('Text body');      
        String[] toAddresses = new String[] {'sampath@thylaksoft.com'};    
        email.setToAddresses(toAddresses);          
        Messaging.SendEmailResult[] sendResult;
        //send the eMail
        sendResult = Messaging.sendEmail(new Messaging.SingleEmailMessage[] { email });
    }
  }
 }
}





public class EmailNotify
{
 public static void SendEmail(Contact[] con)
 {
 
  for (Contact c:con)
  {
   //Date obj = Date.today();
    //Integer n = DAY(TODAY());
    DateTime t = DateTime.now();
    t = t.addDays(1);
    if (t != null)
    {
        Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage();
        email.setSubject('Subject');      
        email.setReplyTo('whoever');
        email.setSaveAsActivity(false);
        email.setPlainTextBody('Text body');      
        String[] toAddresses = new String[] {'sampath@thylaksoft.com'};    
        email.setToAddresses(toAddresses);          
        Messaging.SendEmailResult[] sendResult;
        //send the eMail
        sendResult = Messaging.sendEmail(new Messaging.SingleEmailMessage[] { email });
    }
 
 
 
  }
 }
}