JDesktopPane内のJInternalFrameをJTabbedPaneのタブと入れ替える

Action swapAction = new AbstractAction("JDesktopPane <-> JTabbedPane") {
  @Override public void actionPerformed(ActionEvent e) {
    if (((AbstractButton) e.getSource()).isSelected()) {
      Arrays.stream(desktopPane.getAllFrames())
        .sorted(Comparator.comparing(JInternalFrame::getTitle))
        .forEach(f -> tabbedPane.addTab(f.getTitle(), f.getFrameIcon(), f.getContentPane()));

      JInternalFrame sf = desktopPane.getSelectedFrame();
      if (Objects.nonNull(sf)) {
        tabbedPane.setSelectedIndex(tabbedPane.indexOfTab(sf.getTitle()));
      }
      cardLayout.show(panel, tabbedPane.getClass().getName());
    } else {
      Arrays.stream(desktopPane.getAllFrames())
        .forEach(f -> f.setContentPane(
          (Container) tabbedPane.getComponentAt(tabbedPane.indexOfTab(f.getTitle()))));
      cardLayout.show(panel, desktopPane.getClass().getName());
    }
  }
};