Method error Get in a collection

I need to use XML in a university job and I had problems with a Get method I had to implement in a Collection p>

After a while I took a look at some websites to do this and found the following tutorial , it has a Contact class as follows below with the phones field, and a statement is given to create a Get for her, I created it and the structure was summarized like this:

public class Contato {
     private Collection telefones = new ArrayList();
     public Collection getTelefones() {
         return telefones;
     }
}

But in the code snippet below I got an error:

  

--- Change phone type to Object ---

for (Telefone fone : contato.getTelefones()) {
    tagFone = doc.createElement("Telefone");

    idFone = doc.createElement("id");
    dddFone = doc.createElement("ddd");
    numeroFone = doc.createElement("numero");
    //Insere os valores de telefones nas tags referentes
    idFone.setTextContent(String.valueOf(fone.getId()));
    dddFone.setTextContent(String.valueOf(fone.getDdd()));
    numeroFone.setTextContent(String.valueOf(fone.getNumero()));
    //Insere as tags Telefone na tag Telefone
    tagFone.appendChild(idFone);
    tagFone.appendChild(dddFone);
    tagFone.appendChild(numeroFone);
    //Insere a tag Telefone na tag pai Telefones
    tagFones.appendChild(tagFone);
}

I tried something different but could not solve it. I believe that it is in the Get method that I implemented myself, and if the community can help me, I will be grateful.