CardLayoutカードレイアウト(指定されたカードプレゼンテーションに切り替える)

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

public class CardLayoutChange implements ActionListener {

	JPanel p1, p2, p3, p4;
	int i = 1;
	JFrame f;

	public CardLayoutChange() {

		f = new JFrame();
		Container contentPane = f.getContentPane();
		contentPane.setLayout(new GridLayout(2, 1));

		p1 = new JPanel();
		JButton b = new JButton("Change  Card");
		b.addActionListener(this);
		p1.add(b);
		contentPane.add(p1);

		p2 = new JPanel();
		p2.setLayout(new FlowLayout());
		p2.add(new JButton("first"));
		p2.add(new JButton("second"));
		p2.add(new JButton("third"));
		p3 = new JPanel();
		p3.setLayout(new GridLayout(3, 1));
		p3.add(new JButton("fourth"));
		p3.add(new JButton("fifth"));
		p3.add(new JButton("This  is  the  last  button"));
		p4 = new JPanel();
		p4.setLayout(new CardLayout());
		p4.add("one", p2);
		p4.add("two", p3);
		((CardLayout) p4.getLayout()).show(p4, "one");

		contentPane.add(p4);

		f.setTitle("CardLayout");
		f.pack();
		f.setVisible(true);

		f.addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
	}

	public void actionPerformed(ActionEvent event) {
		switch (i) {
		case 1:
			((CardLayout) p4.getLayout()).show(p4, "two");
			break;
		case 2:
			((CardLayout) p4.getLayout()).show(p4, "one");
			break;
		}
		i++;
		if (i == 3)
			i = 1;
		f.validate();
	}

	public static void main(String args[]) {

		new CardLayoutChange();

	}
}