when I export data to excel, if the workbook like workbook = new XSSFWorkbook(); and apply a cellstyle as code: org.apache.poi.ss.usermodel.CellStyle style = this.workbook.createCellStyle(); style.setHidden(false); org.apache.poi.ss.usermodel.DataFormat excelFormat = this.workbook.createDataFormat(); style.setDataFormat(excelFormat.getFormat(dataFormat)); sheet.setDefaultColumnStyle(i, style); I must use setHidden(false) to see the column in exported excel. But, when workbook = new HSSFWorkbook(); the style hidden property need not to set!
I could not reproduce this problem any more with the latest version so it is likely fixed since some time already. Please re-test with 3.12-beta1 or a recent nightly build and reopen this bug if this is still a problem for you.