Java Box create vertical box

import java.awt.Dimension;
import java.awt.GridLayout;

import javax.swing.Box;
import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Main extends JFrame {

  public Main() {
    JPanel container = new JPanel();

    Box leftBox = Box.createVerticalBox();
    Box centerBox = Box.createVerticalBox();
    Box innerCenter1 = Box.createHorizontalBox();
    Box innerCenter2 = Box.createHorizontalBox();
    Box rightBox = Box.createVerticalBox();

    JPanel rightGrid = new JPanel(new GridLayout(3, 1, 0, 10));

    // LEFT/*from  ww w . j  ava2 s .  c om*/
    leftBox.add(new JCheckBox("Snap to Grid"));
    leftBox.add(new JCheckBox("Show Grid"));

    // CENTER
    innerCenter1.add(new JLabel("X: "));
    innerCenter1.add(new JTextField(3));
    innerCenter2.add(new JLabel("Y: "));
    innerCenter2.add(new JTextField(3));

    centerBox.add(innerCenter1);
    centerBox.add(Box.createRigidArea(new Dimension(0, 10)));
    centerBox.add(innerCenter2);

    // RIGHT
    rightGrid.add(new JButton("Ok"));
    rightGrid.add(new JButton("Cancel"));
    rightGrid.add(new JButton("Help"));
    rightBox.add(rightGrid);

    container.add(leftBox);
    container.add(Box.createRigidArea(new Dimension(10, 0)));
    container.add(centerBox);
    container.add(Box.createRigidArea(new Dimension(10, 0)));
    container.add(rightBox);
    add(container);
  }

  public static void main(String[] args) {
    Main gui = new Main();
    gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    gui.setSize(400, 250);
    gui.setVisible(true);
  }
}