Always show two decimal points in excel cells using Apache poi

This one worked for me:

1. Set Cell Style

   private CellStyle formatDecimalStyle(Workbook workbook, CreationHelper createHelper) {  
       CellStyle style = workbook.createCellStyle();
       style.setDataFormat(createHelper.createDataFormat().getFormat("0.00"));
       return style;   
   }
   

2. Apply Style on Cell

   CellStyle style = formatDecimalStyle(workbook, createHelper);
   Cell creditAmountCell = row.createCell(3);
   creditAmountCell.setCellValue(amount);
   creditAmountCell.setCellStyle(style);
   

In Excel formatting, a # means "place a digit here only if needed", but a 0 means "always place a digit here, even if it's an unnecessary 0". You can specify the data format in Apache POI exactly as you would in Excel itself. If you want the 0 digits to show up, then you need to use 0s as formatting digits. Try

style.setDataFormat(workbook.createDataFormat().getFormat("0.00"));

This will make the value 0 show up as 0.00 and 12.4 as 12.40.