Duvidas no codigo

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


public class SwingExemplo2 extends JFrame implements ActionListener
{
	JButton botao1;
	JPanel panel;
	JTextField texto;
	
	public SwingExemplo2()
	{ 
	    
	
		super("blahblah oO'''");
		  
	}
	
	public void criaJanela()
	{
	   texto = new JTextField("Digite algo...");
	   
	   panel = new JPanel();
	   panel.setLayout(new GridLayout(2,1));
	   
	   botao1 = new JButton("Me clique");
	   botao1.addActionListener(this);
	   
	   panel.add(texto);
	   panel.add(botao1);
	   
	   getContentPane().add(panel,BorderLayout.CENTER);
	   
	   setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	   
	   pack();
	   setVisible(true);
	    	
	}
	
	public void actionPerformed(ActionEvent event)
	{
	  botao1.setText(texto.getText());
	}
	
	public static void main(String[] args) 
	{
       SwingExemplo2 ex2 = new SwingExemplo2();
       ex2.criaJanela();	   
	
	}
}