Created attachment 22834 [details] patch to XSSFSheet implemented setGroupColumnCollapsed() setGroupRowCollapsed() in XSSFSheet and fixed modifiedCellReference() method. added test method and an example of how to group.
Created attachment 22854 [details] new patch added the Apache License in the example file. checked code identation
Thanks for this. I've had to make some changes to it before committing, as a few bits were using 1 based numbers when the method signature was 0 based, but hopefully it's all still working! I've expanded out the tests a little more, so you might want to look at those, and make sure the full form is showing the results you'd expect (the results seem consistent, but I haven't used the API much, so I can't be sure they also make sense....)