public void selectUsers(Object tbl_clients) {
    Object row = ui.getSelectedItem(tbl_clients);

    // TODO: Only Working partially with single selection;
    // Algo is not worth cracking the head

    Object cell = ui.getItem(row, 0);
    ui.remove(cell);
    Client attachedClient = (Client) ui.getAttachedObject(row);
    if (attachedClient.isSelected()) {
      attachedClient.setSelected(false);
      selectedClients.remove(attachedClient);
      markCell(cell, false);
    } else {
      attachedClient.setSelected(true);
      selectedClients.add(attachedClient);
      markCell(cell, true);
    }

    ui.add(row, cell, 0);
  }
  private void markAllCells(boolean choice) {
    Object[] rows = ui.getItems(this.tableClients);

    for (Object row : rows) {
      Object cell = ui.getItem(row, 0);
      ui.remove(cell);
      Client attachedClient = (Client) ui.getAttachedObject(row);
      if (!attachedClient.isSelected()) {
        attachedClient.setSelected(choice);
        markCell(cell, choice);
      }

      ui.add(row, cell, 0);
    }
  }