Merging cells in Excel using Apache POI

I create a method that merge cells and put border if you want.

protected void setMerge(Sheet sheet, int numRow, int untilRow, int numCol, int untilCol, boolean border) {
    CellRangeAddress cellMerge = new CellRangeAddress(numRow, untilRow, numCol, untilCol);
    sheet.addMergedRegion(cellMerge);
    if (border) {
        setBordersToMergedCells(sheet, cellMerge);
    }

}  

protected void setBordersToMergedCells(Sheet sheet, CellRangeAddress rangeAddress) {
    RegionUtil.setBorderTop(BorderStyle.MEDIUM, rangeAddress, sheet);
    RegionUtil.setBorderLeft(BorderStyle.MEDIUM, rangeAddress, sheet);
    RegionUtil.setBorderRight(BorderStyle.MEDIUM, rangeAddress, sheet);
    RegionUtil.setBorderBottom(BorderStyle.MEDIUM, rangeAddress, sheet);
}

You can use :

sheet.addMergedRegion(new CellRangeAddress(startRowIndx, endRowIndx, startColIndx,endColIndx));

Make sure the CellRangeAddress does not coincide with other merged regions as that will throw an exception.

• If you want to merge cells one above another, keep column indexes same
• If you want to merge cells which are in a single row, keep the row indexes same
• Indexes are zero based

For what you were trying to do this should work:

sheet.addMergedRegion(new CellRangeAddress(rowNo, rowNo, 0, 3));

The best answer

sheet.addMergedRegion(new CellRangeAddress(start-col,end-col,start-cell,end-cell));

You can use sheet.addMergedRegion(rowFrom,rowTo,colFrom,colTo);

example sheet.addMergedRegion(new CellRangeAddress(1,1,1,4)); will merge from B2 to E2. Remember it is zero based indexing (ex. POI version 3.12).

for detail refer BusyDeveloper's Guide