JAVAFX LINECHART AND XYSERIES

i created this LineChart (it looks like a scatter chart because the solo points are all indivual XYSeries, there is one actual line -- which is just a series with more than one point), I need to remove the visibiliy of the symbols that are at the ends of the orange line. i have tried to do the following

series.getNode().setStyle("-fx-symbol-visible: false;"); series.getNode().setStyle("visibility: false, -fx-opacity: 0.3;");

series.nodeProperty().get().setStyle("-fx-opacity: 0.3,-fx-symbol-visible: false,-fx-stroke: #ffff00,-fx-stroke-type: centered;");

but the problem is, that it shows that the node is null! why is this?

Data Visualization 6.5 6.0 5.5 5.0 4.0 3.5 3.0 2.5 2.0 0.5 0.0 1.5 -1.0 -0.5 0.0 0.5 1.0 1.52.02.5 3.0 3.5 4.0 4.5 5.0 5.5 O AverageLine O a o d O nine O b o ten o r O f 0 Data Visualization 6.5 6.0 5.5 5.0 4.0 3.5 3.0 2.5 2.0 0.5 0.0 1.5 -1.0 -0.5 0.0 0.5 1.0 1.52.02.5 3.0 3.5 4.0 4.5 5.0 5.5 O AverageLine O a o d O nine O b o ten o r O f 0