if (getItemCount() != 0) setSelectedItem(getItemAt(0));
  public JComboBox(ComboBoxModel model)  {    setEditable(false);    setEnabled(true);    setMaximumRowCount(DEFAULT_MAXIMUM_ROW_COUNT);    setModel(model);    setActionCommand("comboBoxChanged");    // by default set selected item to the first element in the combo box        if (getItemCount() != 0)      setSelectedItem(getItemAt(0));    lightWeightPopupEnabled = true;    isEditable = false;    updateUI();  }