I have made two new pie charts.
One is equivalent to stacked bar chart but for Pie.
the other is a Superimposed pie chart that allow easy comparison between 2 pie chart.
Both are work in progress and do not really fit in the JFreeChart as it should (use of primitive for example).
you can see example here :
"http://www.cs.huji.ac.il/~feit/papers/Spie03TR.pdf" for examples
Fell free to do wathever you want with them.
Any comments are welcome.
All sources are in the jar (4 class).
I have uploaded 2 jpg for those who don't want to download and run the jar.