code: @Override
  	public void actionPerformed(ActionEvent event) {
  		JMenuItem item = (JMenuItem) event.getSource();
  
  		if (item.isSelected()) {
  			showColumn(item.getText());
  		} else {
  			hideColumn(item.getText());
  		}
  	}
docs: /*
  A table column will either be added to the table or removed from the
  table depending on the state of the menu item that was clicked.