MetodoAdicionar

    public void AumentarEstoque(int id, float qntd) {
        String sql = "UPDATE produtos SET qntdEstoque = qntd WHERE id = ?";

        Connection conn = null;
        PreparedStatement x = null;

        try {
            conn = Conexao.createConnectionToMySQL();
            x = conn.prepareStatement(sql);

            x.setInt(1, id);
            x.setFloat(2, qntd);
            x.execute();
        } catch (Exception e) {
            e.printStackTrace();

        } finally {
            try {
                if (x != null) {
                    x.close();
                }
                if (conn != null) {
                    conn.close();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }