An extremely minimal parser for XLSX (Excel) files
I was unable to find a minimal XLSX (Excel) parser. The closest free option would be apache POI with about 8+ megabyte of JARs and features I don't need.
The input is an XLSX file and the output is a Map<String,String[][]> with key of 'sheet name' and a String[][] of cell data.
Dates are reformatted to dd/MM/yyyy (configurable in the code).
The output of String[][] is to keep the interface compatible with CSV (eg. OpenCSV).