trigger ExampleTrigger on Contact (after insert, after delete) {
    if (Trigger.isInsert) {
        Integer recordCount = Trigger.New.size();
        // Call a utility method from another class
        EmailManager.sendMail(xyz@zax.com', 'Trailhead Trigger Tutorial', 
                    recordCount + ' contact(s) were inserted.');
    }
    else if (Trigger.isDelete) {
        // Process after delete
    }
}

public class EmailManager {
    // Public method
    public static void sendMail(String address, String subject, String body) {
        // Create an email message object
        Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
        String[] toAddresses = new String[] {address};
        mail.setToAddresses(toAddresses);
        mail.setSubject(subject);
        mail.setPlainTextBody(body);
        // Pass this email message to the built-in sendEmail method
        // of the Messaging class
        Messaging.SendEmailResult[] results = Messaging.sendEmail(
                                 new Messaging.SingleEmailMessage[] { mail });
       
        // Call a helper method to inspect the returned results
        inspectResults(results);
    }
   
    // Helper method
    private static Boolean inspectResults(Messaging.SendEmailResult[] results) {
        Boolean sendResult = true;
       
        // sendEmail returns an array of result objects.
        // Iterate through the list to inspect results.
        // In this class, the methods send only one email,
        // so we should have only one result.
        for (Messaging.SendEmailResult res : results) {
            if (res.isSuccess()) {
                System.debug('Email sent successfully');
            }
            else {
                sendResult = false;
                System.debug('The following errors occurred: ' + res.getErrors());                
            }
        }
       System.debug('sendResult =' + sendResult);
        return sendResult;
    }
}