code: public void appendWorkSheetRows(WorkSheet worksheet) throws Exception {
  
  		ArrayList<String> newRows = worksheet.getRows();
  
  		this.addRows(newRows, "");
  		for (String col : this.getColumns()) {
  			if (!worksheet.isValidColumn(col)) {
  				continue;
  			}
  			for (String row : newRows) {
  				if (worksheet.isValidColumn(col)) {
  					String value = worksheet.getCell(row, col);
  					this.addCell(row, col, value);
  				}
  
  			}
  		}
  
  	}
docs: Add rows from a second worksheet to be joined by common column. If the
  appended worksheet doesn't contain a column in the master worksheet then
  default value of "" is used. Columns in the appended worksheet not found
  in the master worksheet are not added.
  
  @param worksheet
  @throws Exception