code: public static int copyToSheet(HSSFSheet parentSheet, int parentSheetRow, int parentSheetColumn, HSSFSheet sheet, boolean copyStyle) {
  		int maxColumnNum = 0;
  		Map<Integer, HSSFCellStyle> styleMap = (copyStyle) ? new HashMap<Integer, HSSFCellStyle>() : null;
  		for (int i = sheet.getFirstRowNum(); i <= sheet.getLastRowNum(); i++) {
  			HSSFRow srcRow = sheet.getRow(i);
  			HSSFRow destRow;
  			// subreport is not the first cell in a row
  			if ((parentSheetColumn > 0) && (i == sheet.getFirstRowNum())) {
  				destRow = parentSheet.getRow(parentSheetRow);
  			} else {
  				destRow = parentSheet.getRow(parentSheetRow+i);
  				if (destRow == null) {
  					destRow = parentSheet.createRow(parentSheetRow + i);
  				}
  			}
  			if (srcRow != null) {
  				XlsUtil.copyRow(sheet, parentSheet, parentSheetRow, parentSheetColumn, srcRow, destRow, styleMap);
  				if (srcRow.getLastCellNum() > maxColumnNum) {
  					maxColumnNum = srcRow.getLastCellNum();
  				}
  			}
  		}
  		for (int i = 0; i <= maxColumnNum; i++) {
  			parentSheet.setColumnWidth(i, sheet.getColumnWidth(i));
  		}
  		return maxColumnNum;
  	}
docs: Copy a sheet to another sheet at a specific (row, column) position
  
  @param parentSheet the sheet to copy into
  @param parentSheetRow the row inside parentSheet where we start to copy
  @param parentSheetColumn the column inside parentSheet where we start to copy
  @param sheet the sheet that is copied
  @param copyStyle true to copy the style
  @return column number