如何让2个JPanels同时滚动？

import javax.swing.*;
import java.awt.*;

public class ScrollablePanelsExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Scrollable Panels Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 300);

        JPanel panel1 = new JPanel();
        panel1.setPreferredSize(new Dimension(400, 500));
        panel1.setBackground(Color.RED);

        JPanel panel2 = new JPanel();
        panel2.setPreferredSize(new Dimension(400, 500));
        panel2.setBackground(Color.BLUE);

        JPanel container = new JPanel();
        container.setLayout(new GridLayout(2, 1));

        JScrollPane scrollPane1 = new JScrollPane(panel1);
        scrollPane1.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
        scrollPane1.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

        JScrollPane scrollPane2 = new JScrollPane(panel2);
        scrollPane2.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
        scrollPane2.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

        container.add(scrollPane1);
        container.add(scrollPane2);

        frame.add(container);
        frame.setVisible(true);
    }
}