code: @Override
  	public String getToolTipText(final MouseEvent event) {
  		final int row = rowAtPoint(event.getPoint());
  		final int column = columnAtPoint(event.getPoint());
  		if (row != -1 && column != -1) {
  			String tip = super.getToolTipText(event);
  			if (tip == null) {
  				tip = getTextAt(row, column);
  				if (tip == null || tip.length() == 0) { // NOPMD
  					tip = super.getToolTipText();
  				}
  			}
  			return tip;
  		}
  		return super.getToolTipText();
  	}
docs: {@inheritDoc}