JAVA: Layout de Fluxo 03 (PG 291)

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

public class GerenciadoresLayout {
    public static void main(String[] args) {
        GerenciadoresLayout sistema = new GerenciadoresLayout();
        sistema.iniciar();
    }
    public void iniciar() {
        JFrame janela = new JFrame();
        JPanel painel = new JPanel();

        painel.setBackground(Color.darkGray);

        JButton east = new JButton("east");
        JButton west = new JButton("west");
        JButton north = new JButton("Nort");
        JButton south = new JButton("South");
        JButton center = new JButton("Center");
        JButton center1 = new JButton("center1");

        janela.getContentPane().add(BorderLayout.CENTER, painel);
        painel.add(center);
        painel.add(center1);

        janela.getContentPane().add(BorderLayout.WEST, west);
        janela.getContentPane().add(BorderLayout.NORTH, north);
        janela.getContentPane().add(BorderLayout.SOUTH, south);
        janela.getContentPane().add(BorderLayout.EAST, east);

        janela.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        janela.setSize(200,200);
        janela.setVisible(true);
    }

}