if(dataModel instanceof MutableComboBoxModel) {
if (dataModel instanceof MutableComboBoxModel)
  public void removeItemAt(int index)  {	if(dataModel instanceof MutableComboBoxModel) {    ((MutableComboBoxModel) dataModel).removeElementAt(index);	} else {		throw new RuntimeException("Unable to remove the item because the data model it is not an instance of MutableComboBoxModel.");	}  }