Using Excel Pivot Table Correctly

https://exceljet.net/things-to-know-about-excel-pivot-tables
https://exceljet.net/blog/can-pivot-tables-save-your-job

http://www.excel-easy.com/data-analysis/pivot-tables.html
https://exceljet.net/tips/what-is-a-pivot-table


Apache POI
http://thinktibits.blogspot.sg/2014/08/Create-Pivot-Table-Java-Apache-POI-Example.html