Line not displaying on LineChart in Netbeans IDE - netbeans

Question

The JFreeChart I have created is a LineChart. the problem I am having is that the line on the graph is not showing.
Can anyone tell me why this is occuring.
Here is the coding for the button:
DefaultCategoryDataset dataset2 = new DefaultCategoryDataset();
dataset2.setValue(100, "John B","EMP0001");
dataset2.setValue(200, "John A","EMP0003");
JFreeChart chart2 = ChartFactory.createLineChart("Comission", "Employee", "Number of Sales", dataset2, PlotOrientation.VERTICAL, false, true, true);
chart2.setBackgroundPaint(Color.YELLOW);
chart2.getTitle().setPaint(Color.RED);
CategoryPlot p2 = chart2.getCategoryPlot();
p2.setRangeGridlinePaint(Color.BLUE);
ChartFrame frame2 = new ChartFrame("Employee Comission", chart2);
frame2.setVisible(true);
frame2.setSize(450,350);
This is what happens when the line chart is created:
Line chart without line displaying on chart
Please could someone help just indicate to me where the possible problem lies.

Answer 1

In order to show a line you need to have two data items that have the same value for the rowKey and different values for the column key.
if you change the data to:
dataset2.setValue(100, "John A","EMP0000");
dataset2.setValue(200, "John A","EMP0001");
dataset2.setValue(300, "John B","EMP0002");
dataset2.setValue(400, "John B","EMP0004");
then in plots :
Notice that the "John A" values are red and the "John B" values are blue and
the red and blue do not connect. The column values are printed along the bottom.