content: package tim.prune.save;
  
  import javax.swing.JButton;
  import javax.swing.ListSelectionModel;
  import javax.swing.event.ListSelectionEvent;
  import javax.swing.event.ListSelectionListener;
  
  
  /**
   * Class to enable and disable a pair of up and down buttons
   */
  public class UpDownToggler implements ListSelectionListener
  {
  	private final JButton _upButton;
  	private final JButton _downButton;
  	private int _maxIndex = 2;
  
  	/**
  	 * Constructor giving buttons to enable/disable
  	 * @param inUpButton up button
  	 * @param inDownButton down button
  	 */
  	public UpDownToggler(JButton inUpButton, JButton inDownButton)
  	{
  		_upButton = inUpButton;
  		_downButton = inDownButton;
  	}
  
  	/**
  	 * Set the list size
  	 * @param inListSize number of items in list
  	 */
  	public void setListSize(int inListSize)
  	{
  		_maxIndex = inListSize - 1;
  	}
  
  	/**
  	 * list selection has changed
  	 */
  	public void valueChanged(ListSelectionEvent e)
  	{
  		ListSelectionModel lsm = (ListSelectionModel) e.getSource();
  		if (lsm.isSelectionEmpty())
  		{
  			// no rows are selected
  			_upButton.setEnabled(false);
  			_downButton.setEnabled(false);
  		}
  		else
  		{
  			// single row is selected
  			int row = lsm.getMinSelectionIndex();
  			_upButton.setEnabled(row > 0);
  			_downButton.setEnabled(row >= 0 && row < _maxIndex);
  		}
  	}
  }
  