import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class MyFrame extends JFrame {

	private static final long serialVersionUID = 1L;
	JPanel pane;
	JPanel pane2;
	JButton button;
	JLabel label;
	
	public MyFrame() {
		super();
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		pane = new JPanel();
		button = new JButton("A");
		label = new JLabel("B");
		button.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				pane2 = new JPanel();
				pane2.add(label);
				setContentPane(pane2);
			}
		});
		pane.add(button);
		setSize(200,200);
		this.setContentPane(pane);
	}
	
	public static void main(String[] args) {
		MyFrame frame = new MyFrame();
		frame.setVisible(true);

	}

}