Java swing help needed

[AdRock]

I am trying to learn how to create user interfaces using Java Swing and I've been able to add combo boxs, text fields, labels etc but now i'm stuck.

I am trying to add a panel (or at least something that I can add graphics to such as circles or squares....anything) but when I run my program the graphics aren't showing.

How do i add a panel so that the graphics show. What i did get to show was a tiny little square when the background color was set to purple but nothing you can put anything onto.

I have tried creating a class to extend the JPanel but it doesn't work even thought it compiles.

This is just a test program to help me learn

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

class SwingWindow extends JFrame
{
	public SwingWindow()
	{
		super("Hello from Java Swing");
		setSize(300, 100);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setVisible(true);
		
		Container contentArea = getContentPane();
		contentArea.setBackground(Color.white);
		
		FlowLayout flowManager = new FlowLayout();
		contentArea.setLayout(flowManager);
		
		JComboBox islands = new JComboBox();
		islands.addItem("Corfu");
		islands.addItem("Kefalonia");
		islands.addItem("Crete");
		islands.addItem("Rhodes");
		islands.addItem("Paxos");
		islands.addItem("Mykonos");
		
		contentArea.add(islands);										
		
		JButton playButton = new JButton("Play");
		contentArea.add(playButton);
		
		JButton pauseButton = new JButton("Pause");
		contentArea.add(pauseButton);
		
		JButton stopButton = new JButton("Stop");
		contentArea.add(stopButton);
		
		JLabel textLabel = new JLabel("Fun programming :");
		contentArea.add(textLabel);
		
		JTextField text = new JTextField("", 15);
		contentArea.add(text);
		
		CustomPanel panel = new CustomPanel();
		contentArea.add(panel);
		
		setContentPane(contentArea);				
	}
	
	class CustomPanel extends JPanel
	{
		public void paintComponent(Graphics painter)
		{
			painter.setColor(Color.white);
			painter.fillRect(0,0,getSize().width, getSize().height);
			Font currentFont = new Font("Serif",Font.BOLD,24);
			painter.setFont(currentFont);
			
			Color customPurple = new Color(128,0,128);
			painter.setColor(customPurple);
			painter.drawString("A painted panel", 20, 40);
		}
	}
}

public class HelloSwing
{
	public static void main(String[] args)
	{
		SwingWindow Hello = new SwingWindow();
	}
}

[Arkie_student]

Add:
setVisible(true);

Below:
setContentPane(contentArea);

[AdRock]

I tried adding that but it didn't make any difference. I also set the colour of the extened panel to red and all it does is display a tiny red square