Recommended Java maths/stats library

Can someone recommend a good statistics library for Java - it must include the ability to calculate the correlation of two data sets.

I have been trying to compute the correlation of two ArrayLists - for some reason I am getting an incorrect answer (checked in Excel) despite what seems to be sound logic.

I found one at jfree.org which provides a single class called Statistics which includes what I need for now. But if you know of others, please let me know as I'd rather use the best option from the start, rather than changing the code later.

From stackoverflow

• I suggest you use Apache Commons Math library. It has a correlation package.

  Ankur : Just wondering, have you used this. The docs suggest that the Correlation class exists, however when I import the .jar it does not resolve and looking at the source I can't see a correlation class anywhere?

  Aziz : the correlation package is added to version 2.0. Make sure your download the correct version :)

  Aziz : I think you should use SVN to get version 2.0 (couldn't find download links on the website)