Send attachment Via Apex using Templates

Email Via Apex using Email Templates :

Contact con = [Select id from contact Limit 1];

List<String> emailsAll = new List<String>();
emailsAll.add('toEmailAddress@gmail.com');

List<String> emailsCC = new List<String>();
emailsCC.add('cCEmailAddress@gmail.com');

String TemplateId = [SELECT Id FROM EmailTemplate WHERE DeveloperName = 'Multi_Language_Template_Test' LIMIT 1].Id;

List<Messaging.SingleEmailMessage> mails =  new List<Messaging.SingleEmailMessage>();   
       
        // Step 1: Create a new Email
        Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
       
        // Step 2: Set list of people who should get the email
        mail.setToAddresses(emailsAll);
        mail.setCcAddresses(emailsCC);

        // Step 3: Set who the email is sent from
        mail.setReplyTo('noreply@gmail.com'); // change it with your/Company mail address.
        mail.setSenderDisplayName('Salesforce User');

       //Step 4 : when Using Template Id 
       mail1.setTargetObjectId(con.Id); //Mandatory while using Template(ID of  contact, lead, or user)
       mail1.setTemplateId(TemplateId);
                  /*OR*/
        // Step 4. Set email contents - you can use variables! when not using Template
        mail.setSubject(mSubject);
        mail.setHtmlBody(mbody);

        // Step 5. Attach file!  (Not Mendatory)
        List<Messaging.Emailfileattachment> fileAttachments = new   List<Messaging.Emailfileattachment>();
        for (Attachment a : [select Name, Body, BodyLength from Attachment where ParentId =: parentId ORDER BY CreatedDate DESC Limit : 1])
        {
            Messaging.Emailfileattachment efa = new Messaging.Emailfileattachment();
            efa.setFileName(a.Name);
            efa.setBody(a.Body);
            fileAttachments.add(efa);
        }
        mail.setFileAttachments(fileAttachments);

        // Step 6. Add your email to the master list
        mails.add(mail);

        // Step 7: Send all emails in the master list
        Messaging.sendEmail(mails);