JasperReport, always get blank PDF?

 
line below with new JREmptyDataSource() will get pdf as per expected.

jasperPrint = JasperFillManager.fillReport(report, jrParam, new JREmptyDataSource());



vs

where as using static _DATA_SOURCE_EMPTY, will always get blank pdf.

private static JREmptyDataSource _DATA_SOURCE_EMPTY = new JREmptyDataSource();

...

jasperPrint = JasperFillManager.fillReport(report, jrParam, _DATA_SOURCE_EMPTY);

...