question: protected void drawDomainCrosshair ( Graphics2D g2 , Rectangle2D dataArea , PlotOrientation orientation , int datasetIndex , Comparable rowKey , Comparable columnKey , Stroke stroke , Paint paint ) { CategoryDataset dataset = getDataset ( datasetIndex ) ; CategoryAxis axis = getDomainAxisForDataset ( datasetIndex ) ; CategoryItemRenderer renderer = getRenderer ( datasetIndex ) ; Line2D line ; if ( orientation == PlotOrientation . VERTICAL ) { double xx = renderer . getItemMiddle ( rowKey , columnKey , dataset , axis , dataArea , RectangleEdge . BOTTOM ) ; line = new Line2D . Double ( xx , dataArea . getMinY ( ) , xx , dataArea . getMaxY ( ) ) ; } else { double yy = renderer . getItemMiddle ( rowKey , columnKey , dataset , axis , dataArea , RectangleEdge . LEFT ) ; line = new Line2D . Double ( dataArea . getMinX ( ) , yy , dataArea . getMaxX ( ) , yy ) ; } g2 . setStroke ( stroke ) ; g2 . setPaint ( paint ) ; g2 . draw ( line ) ; }
target:  Draws a domain crosshair.