Apache POI Excel - how to configure columns to be expanded?

If you want to auto size all columns in a workbook, here is a method that might be useful:

public void autoSizeColumns(Workbook workbook) {
    int numberOfSheets = workbook.getNumberOfSheets();
    for (int i = 0; i < numberOfSheets; i++) {
        Sheet sheet = workbook.getSheetAt(i);
        if (sheet.getPhysicalNumberOfRows() > 0) {
            Row row = sheet.getRow(sheet.getFirstRowNum());
            Iterator<Cell> cellIterator = row.cellIterator();
            while (cellIterator.hasNext()) {
                Cell cell = cellIterator.next();
                int columnIndex = cell.getColumnIndex();
                sheet.autoSizeColumn(columnIndex);
            }
        }
    }
}

After you have added all your data to the sheet, you can call autoSizeColumn(int column) on your sheet to autofit the columns to the proper size

Here is a link to the API.

See this post for more reference Problem in fitting the excel cell size to the size of the content when using apache poi

Tip : To make Auto size work , the call to sheet.autoSizeColumn(columnNumber) should be made after populating the data into the excel.

Calling the method before populating the data, will have no effect.