public override bool Equals(object obj)
        {
            bool iguals = true;
            int posicio = 0;
            if (obj == null)
            {
                return this == null;
            }
            if (!(obj is TipusBase))
            {
                return false;
            }
            Pila<TipusBase> comparada = (Pila<TipusBase>)obj;
            return base.Equals(obj);

            if (this.nElem != comparada.nElem)
            {
                iguals = false;
            }
            else
            {
                while (iguals && posicio < nElem)
                {
                    iguals = object.Equals(dades[posicio], comparada.dades[posicio]);
                    posicio++;
                }
            }
            return iguals;
        }