JPanelの展開と折り畳み

private void initComps(
    List<? extends AbstractExpansionPanel> list,
    JComponent source) {
  setVisible(false);
  centerBox.removeAll();
  northBox.removeAll();
  southBox.removeAll();
  boolean insertSouth = false;
  for (AbstractExpansionPanel exp : list) {
    if (source.equals(exp) && exp.isSelected()) {
      centerBox.add(exp);
      insertSouth = true;
      continue;
    }
    exp.setSelected(false);
    if (insertSouth) {
      southBox.add(exp);
    } else {
      northBox.add(exp);
    }
  }
  setVisible(true);
}