private static int exist (Opinion opinion) {
		int i;
		Opinion opinion_tmp;
		for (i = 0; i < opinion_lst.size(); i++) {
			opinion_tmp = opinion_lst.get (i);
			if (opinion_tmp.getMarca ().equals (opinion.getMarca ()) &&
				opinion_tmp.getModelo ().equals (opinion.getModelo ()) &&
				opinion_tmp.getAuthor ().equals (opinion.getAuthor ()) &&
				opinion_tmp.getValoracion () == opinion.getValoracion () &&
				opinion_tmp.getLoMejor ().equals (opinion.getLoMejor ()) &&
				opinion_tmp.getLoPeor ().equals (opinion.getLoPeor ()) &&
				opinion_tmp.getOpinion ().equals (opinion.getOpinion ()))
				return 1;
		}

		return 0;
	}