Convert java DateFormat patterns into Excel custom number formats.
For example, to format a date in excel using the "dd MMMM, yyyy" pattern and Japanese
locale, use the following code:
// returns "[$-0411]dd MMMM, yyyy;@" where the [$-0411] prefix tells Excel to use the Japanese locale
String excelFormatPattern = DateFormatConverter.convert(Locale.JAPANESE, "dd MMMM, yyyy");
CellStyle cellStyle = workbook.createCellStyle();
DataFormat poiFormat = workbook.createDataFormat();
cellStyle.setDataFormat(poiFormat.getFormat(excelFormatPattern));
cell.setCellValue(new Date());
cell.setCellStyle(cellStyle); // formats date as '2012年3月17日'
TODO Generalise this for all Excel format strings