best opensource graph API to integrate with java

Suggest me a best opensource graph API to integra开发者_开发技巧te with java application. Basically it collects and stores some data.This collected data should be drawn in a graph like mothly average of data flow , weekly average ...The API should support extensive graph types like bar chart,pie chart , custom chart etc.,

I have used the JFreeChart library for my charting needs. You still need to take care of storing the data yourself, though.

JFreeChart is definitely a good one. You might find the following resources useful on understanding how to get started.

Gantt Chart http://sanjaal.com/java/?p=343

3D Category Bar Chart http://sanjaal.com/java/?p=321

3D Pie Chart http://sanjaal.com/java/?p=318

Go through the API documentations. You will definitely find it worth using.