What is the best open-source java charting library? (other than jfreechart)

There is charts4j which is a charts and graphs API. It enables developers to programmatically create the charts available in the Google Chart API through a straightforward and intuitive Java API.

Disclaimer: I wrote charts4j. We will be doing another major release in the next few weeks.

There aren't a lot of them because they would be in competition with JFreeChart, and it's awesome. You can get documentation and examples by downloading the developer's guide. There are also tons of free online tutorials if you search for them.

• JFreeChart - Tutorial
• Introduction to JFreeChart