question: @ Override public void drawDomainGridline ( Graphics2D g2 , CategoryPlot plot , Rectangle2D dataArea , double value ) { Line2D line = null ; PlotOrientation orientation = plot . getOrientation ( ) ; if ( orientation == PlotOrientation . HORIZONTAL ) { line = new Line2D . Double ( dataArea . getMinX ( ) , value , dataArea . getMaxX ( ) , value ) ; } else if ( orientation == PlotOrientation . VERTICAL ) { line = new Line2D . Double ( value , dataArea . getMinY ( ) , value , dataArea . getMaxY ( ) ) ; } Paint paint = plot . getDomainGridlinePaint ( ) ; if ( paint == null ) { paint = CategoryPlot . DEFAULT_GRIDLINE_PAINT ; } g2 . setPaint ( paint ) ; Stroke stroke = plot . getDomainGridlineStroke ( ) ; if ( stroke == null ) { stroke = CategoryPlot . DEFAULT_GRIDLINE_STROKE ; } g2 . setStroke ( stroke ) ; g2 . draw ( line ) ; }
target:  Draws a grid line against the domain axis. <P> Note that this default implementation assumes that the horizontal axis is the domain axis. If this is not the case, you will need to override this method.