JFrameの位置・サイズを記憶する

public MainPanel(JFrame frame) {
  super(new BorderLayout());
  this.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
  this.prefs = Preferences.userNodeForPackage(getClass());
  frame.addWindowListener(new WindowAdapter() {
    @Override public void windowClosing(WindowEvent e) {
      saveLocation();
      e.getWindow().dispose();
    }
  });
  frame.addComponentListener(new ComponentAdapter() {
    @Override public void componentMoved(ComponentEvent e) {
      JFrame frame = (JFrame) e.getComponent();
      if (frame.getExtendedState() == Frame.NORMAL) {
        Point pt = frame.getLocationOnScreen();
        if (pt.x < 0 || pt.y < 0) {
          return;
        }
        try {
          pos.setLocation(pt);
        } catch (IllegalComponentStateException icse) {
          icse.printStackTrace();
        }
      }
    }

    @Override public void componentResized(ComponentEvent e) {
      JFrame frame = (JFrame) e.getComponent();
      if (frame.getExtendedState() == Frame.NORMAL) {
        dim.setSize(getSize());
      }
    }
  });
  Box box = Box.createHorizontalBox();
  box.add(Box.createHorizontalGlue());
  box.add(clearButton);
  box.add(Box.createHorizontalStrut(2));
  box.add(exitButton);
  add(new JLabel("TEST"));
  add(box, BorderLayout.SOUTH);
  int wdim = prefs.getInt(PREFIX + "dimw", dim.width);
  int hdim = prefs.getInt(PREFIX + "dimh", dim.height);
  dim.setSize(wdim, hdim);
  setPreferredSize(dim);
  Rectangle screen = frame.getGraphicsConfiguration().getBounds();
  pos.setLocation(screen.x + screen.width / 2 - dim.width / 2,
                  screen.y + screen.height / 2 - dim.height / 2);
  int xpos = prefs.getInt(PREFIX + "locx", pos.x);
  int ypos = prefs.getInt(PREFIX + "locy", pos.y);
  pos.setLocation(xpos, ypos);
  frame.setLocation(pos.x, pos.y);
}

private void saveLocation() {
  prefs.putInt(PREFIX + "locx", pos.x);
  prefs.putInt(PREFIX + "locy", pos.y);
  prefs.putInt(PREFIX + "dimw", dim.width);
  prefs.putInt(PREFIX + "dimh", dim.height);
  try {
    prefs.flush();
  } catch (BackingStoreException e) {
    e.printStackTrace();
  }
}