@Override
  public void exchangeRows(int idx1, int idx2) {
    Collections.swap(myItems, idx1, idx2);
    if (idx1 < idx2) {
      fireTableRowsUpdated(idx1, idx2);
    }
    else {
      fireTableRowsUpdated(idx2, idx1);
    }
  }
@Override
  public void exchangeRows(int idx1, int idx2)