Java Swing - 如何获取所有者窗口和根

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Container;
import java.awt.Window;

import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
import javax.swing.plaf.basic.BasicComboPopup;

public class Main extends JPanel  {

  private JComboBox comboBox;

  public Main() {
    comboBox = new JComboBox(new String[] { "Select Pet", "Bird", "Cat", "Dog", "Rabbit",
        "Pig", "Other" });
    add(comboBox, BorderLayout.PAGE_START);
    JFrame frame = new JFrame("Main");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.add(comboBox);
    frame.pack();
    frame.setVisible(true);

    comboBox.showPopup();
    Object child = comboBox.getAccessibleContext().getAccessibleChild(0);
    BasicComboPopup popup = (BasicComboPopup) child;
    popup.setName("BasicComboPopup");
    JList list = popup.getList();
    Container c = SwingUtilities.getAncestorOfClass(JScrollPane.class, list);
    JScrollPane scrollPane = (JScrollPane) c;

    Window mainFrame = SwingUtilities.windowForComponent(comboBox);

    System.out.println(mainFrame.getName());
    Window popupWindow = SwingUtilities.windowForComponent(popup);
    System.out.println(popupWindow);
    Window popupWindowa = SwingUtilities.windowForComponent(c);
    System.out.println(popupWindowa);

    Window mainFrame1 = SwingUtilities.getWindowAncestor(comboBox);

    System.out.println(mainFrame1);
    Window popupWindow1 = SwingUtilities.getWindowAncestor(popup);
    System.out.println(popupWindow1);

    Component mainFrame2 = SwingUtilities.getRoot(comboBox);

    System.out.println(mainFrame2.getName());
    Component popupWindow2 = SwingUtilities.getRoot(popup);
    System.out.println(popupWindow2);

    if (popupWindow != mainFrame) {
      popupWindow.pack();
    }
  }

  public static void main(String[] args) {
    Main Main = new Main();
  }
}