Elements not showing up in java GUI

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Java

GUI

I'm working on a program for pizza orders with a GUI. My problem is that when I run the GUI, some of the elements won't show up. I'm pretty sure the problem is with the. 'BorderLayout.DIRECTION' bits. Only one item with each direction (north,south, etc) will show up. What i'm wondering is how I can fix that to make sure everything shows ups.

import java.awt.BorderLayout;
import java.awt.Container;

import javax.swing.JButton;
import javax.swing.JCheckBox;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.JTextField;


public class PizzaOrder {

	 private JComboBox createToppingsMenu() {
 		JComboBox comboBox = new JComboBox();
 		comboBox.addItem("Pepperoni");
 		comboBox.addItem("Sausage");
 		comboBox.addItem("Pinapple");
 		return comboBox;
 	}

	 private JComboBox createGetMenu() {
		JComboBox combo1Box = new JComboBox();
		combo1Box.addItem("Delivery");
		combo1Box.addItem("Pick Up");
		return combo1Box;
	}

	private JPanel createNamePanel() {
		JPanel namePanel = new JPanel();
		namePanel.add (new JLabel("Name:  "));
		namePanel.add (new JTextField(15));
		return namePanel;
	}

	private JPanel createAddressPanel() {
		JPanel addressPanel = new JPanel();
		addressPanel.add (new JLabel("Address:  "));
		addressPanel.add (new JTextField(15));
		return addressPanel;
	}

	private JPanel createPhonePanel() {
		JPanel phonePanel = new JPanel();
		phonePanel.add (new JLabel("Phone Number:  "));
		phonePanel.add (new JTextField(15));
		return phonePanel;
	}



	private JPanel createButtonPanel() {
		JPanel buttonPanel = new JPanel();
		buttonPanel.add (new JButton("Place order"));
		buttonPanel.add (new JButton("Cancel order"));
		return buttonPanel;
	}

	public static void main(String[] args) {
		JFrame f = new JFrame();
		f.setTitle("Pizza Order");

		PizzaOrder order = new PizzaOrder();
		Container contentPane = f.getContentPane();

		JPanel namePanel = order.createNamePanel();
		contentPane.add(namePanel, BorderLayout.SOUTH);

		JPanel addressPanel = order.createAddressPanel();
		contentPane.add(addressPanel, BorderLayout.SOUTH);

		JPanel phonePanel = order.createPhonePanel();
		contentPane.add(phonePanel, BorderLayout.SOUTH);

		JComboBox comboBox = order.createToppingsMenu();
		contentPane.add(comboBox, BorderLayout.CENTER);

		JComboBox combo1Box = order.createGetMenu();
		contentPane.add(combo1Box, BorderLayout.CENTER);

		JPanel buttonPanel = order.createButtonPanel();
		contentPane.add(buttonPanel, BorderLayout.EAST);

		f.setSize(500, 500);

		f.setVisible(true);

	}

}

What I have tried:

looking it up but I haven't been able to figure anything out.