private void LerBDMateriaPrimaComboBox(JComboBox ComboBoxMateriaPrima) {
       
        ComboBoxMateriaPrima.removeAllItems();
        //CARREGAR DADOS
        Set<String> opcao = new HashSet<String>();

        try {
            Class.forName("org.apache.derby.jdbc.ClientDriver");

        } catch (ClassNotFoundException e) {
            System.err.print("ClassNotFoundException: ");
            System.err.println(e.getMessage());
            System.out.println("O driver expecificado nao foi encontrado.");
        }

        try {
            con = DriverManager.getConnection(url);
            String nomeTabela = "MATERIA_PRIMA";
            String sql = "SELECT * FROM " + nomeTabela;
            PreparedStatement st = (PreparedStatement) con.prepareStatement(sql);
            ResultSet rs = st.executeQuery();

            while (rs.next()) {
                opcao.add(rs.getString("NOME"));
            }
            st.close();
            con.close();

        } catch (SQLException ex) {
            System.err.println("SQLException: " + ex.getMessage());
        }

        ComboBoxMateriaPrima.addItem("--Materia Prima--");
        Iterator<String> it = opcao.iterator();
        while (it.hasNext()) {
            ComboBoxMateriaPrima.addItem(it.next());
        }

    }