Java AWT BorderLayout fill all area

import java.awt.BorderLayout;

import javax.swing.JButton;
import javax.swing.JFrame;

public class Main {

  public static void main(String[] args) {
    JFrame frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setTitle("BorderLayout frame");
    //w w  w  . j av a 2 s .  c om
    /* Since the default layout manager for bordered containers is
     * already a BorderLayout, the following line is OPTIONAL here.
     */
    frame.getContentPane().setLayout(new BorderLayout());
    
    frame.getContentPane().add(new JButton("NORTH"),  BorderLayout.NORTH);
    // ... or BorderLayout.PAGE_START

    frame.getContentPane().add(new JButton("WEST"),   BorderLayout.WEST);
    // ... or BorderLayout.LINE_START

    frame.getContentPane().add(new JButton("EAST"),   BorderLayout.EAST);
    // ... or BorderLayout.LINE_END

    frame.getContentPane().add(new JButton("SOUTH"),  BorderLayout.SOUTH);
    // ... or BorderLayout.PAGE_END

    frame.getContentPane().add(new JButton("CENTER"), BorderLayout.CENTER);
    frame.pack();
    frame.setVisible(true);
  }
}