jtable example

 while(rs.next()){
     Vector<String> rowData = new Vector<>();
      rowData.add(rs.getString(1));
      rowData.add(rs.getString(2));
      rowData.add(rs.getString(3));

      model.addRow(rowData);
 }
//after the loop count the sum of 3rd column

int total=0;
for (int i = 0; i < model.getRowCount(); i++){
    total +=Integer.parseInt( model.getValueAt(i, 2).toString() );// 3rd column . row column indexes are 0 based
}

System.out.println("sum of 3rd line is "+total);