From dev mailing list [1] Replace SXSSFRow's data structure for storing SXSSFCells with a TreeMap, which uses less memory than an Array for sparse spreadsheets, reduces the number of lines of code, and is faster for some methods (trivially slower for others). Since the purpose of the streaming workbook API is to have a lower memory footprint and not speed, this seems like a good tradeoff. [1] https://mail-archives.apache.org/mod_mbox/poi-dev/201511.mbox/%3CCABdJj57-Z1sMtdTXdTj8-r_PJ2TmRFHJ%3DM2RfHUU49hiATgW7Q%40mail.gmail.com%3E
Added in r1717192 and r1717195. No need to update changes.html since this is internal to POI.
On second thought, this change might affect the memory consumption or speed of SXSSFWorkbooks, which users should know about in case they notice an increase or decrease in memory or speed. Update change log in r1717196.