仅显示最后添加的组件的BoxLayout

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

public class LastComponentOnly {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Last Component Only Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 200);

        JPanel panel = new JPanel();
        panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS));

        JButton button1 = new JButton("Button 1");
        JButton button2 = new JButton("Button 2");
        JButton button3 = new JButton("Button 3");

        panel.add(button1);
        panel.add(button2);
        panel.add(button3);

        // 仅显示最后添加的组件
        Component[] components = panel.getComponents();
        for (int i = 0; i < components.length - 1; i++) {
            panel.remove(components[i]);
        }
        panel.revalidate();
        panel.repaint();

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