if (model == null) throw new IllegalArgumentException("Null 'model' argument.");
  public void setModel(ListModel model)  {    if (this.model == model)      return;        if (this.model != null)      this.model.removeListDataListener(listListener);        ListModel old = this.model;    this.model = model;        if (this.model != null)      this.model.addListDataListener(listListener);        firePropertyChange("model", old, model);    revalidate();    repaint();  }