private void showInvoice() {
    // Get the currently selected subscription
    int rowNumber = jTable1.convertRowIndexToModel(jTable1.getSelectedRow());
    String invoiceId = (String) model.getValueAt(rowNumber, 0);
    Invoice invoice = new Invoice();
    invoice.readInvoice(Integer.parseInt(invoiceId));

    // Show popup
    Application.getInstance().showPopup(new InvoicePopup(invoice));
  }