private void VooraadknopActionPerformed(java.awt.event.ActionEvent evt) {
    DefaultTableModel model = (DefaultTableModel) jTable1.getModel();
    model.setRowCount(0);

    List<Product> producten = WinkelApplication.getQueryManager().getVoorraad();
    for (Product p : producten) {
      model.addRow(new Object[] {p.getProductId(), p.getName(), p.getAantal()});
    }
  }
  private void terugKnopMouseClicked(java.awt.event.MouseEvent evt) {

    WinkelApplication.getInstance().showPanel(new view.AlgemeneTaken(null));
  }