Thx to David's help, I can draw a contour chart with symbolic axis now, but it can't draw the gridelines.
I found that the ContourPlot don't have the setDomainGridlinesVisible and setRangeGridlinesVisible functions like XYPlot, is that means ContourPlot don't support gridlines?
I have also tried to use
SymbolicAxis.setSymbolicGridLinesVisible function to set the gridlines visible, but the chart just don't show any gridelines...
Cheers,
Andy