Low memory writing/reading with Apache POI

Question

I\'m trying to write a pretty large XLSX file (4M+ cells) and I\'m having some memory issues.

I can\'t use SXSSF since I also need to read the existing cells in the

Answer 1

To handle large data with low memory, the best and I think the only option is SXSSF api-s. If you need to read some data of the existing cells, I assume you do not need the entire 4M+ at the same time. In such a case based on your application requirement, you can handle the window size yourself and keep in memory only the amount of data you need at a particular time. You can start by looking at the example at : http://poi.apache.org/spreadsheet/how-to.html#sxssf

Something as

SXSSFWorkbook wb = new SXSSFWorkbook(-1); // turn off auto-flushing and accumulate all rows in memory
// manually control how rows are flushed to disk 
if(rownum % NOR == 0) {
((SXSSFSheet)sh).flushRows(NOR); // retain NOR last rows and flush all others

Hope this helps.