I am looking to write to an excel (.xls MS Excel 2003 format) file programatically using Java. The excel output files may contain ~200,000 rows which I plan to split over n
All existing Java APIs try to build the whole document in RAM at once. Try to write an XML file which conforms to the new xslx file format instead. To get you started, I suggest to build a small file in the desired form in Excel and save it. Then open it and examine the structure and replace the parts you want.
Wikipedia has a good article about the overall format.