Thread: JList - Learning Java

HI, I'm learning Java but I got a problem when I'm using JList - but I don't know what it is.

My Main-Class:

import javax.swing.JFrame;
 
import GUI_JComboBox.Gui;
 
public class Main {
 
	public static void main(String[] args) {
 
		Gui go = new Gui();
		go.setSize(300, 200);
		go.setVisible(true);
		go.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
 
	}
 
}

My Gui Class:

import javax.swing.*;
 
import java.awt.*;
 
import javax.swing.event.*;
 
@SuppressWarnings("serial")
public class Gui extends JFrame{
 
	private JList list;
	private static String[] colornames = {"black", "blue", "red", "white"};
	private static Color[] colors = {Color.BLUE, Color.BLACK, Color.WHITE, Color.RED};
 
	public Gui(){
		super("JList");
		setLayout(new FlowLayout());
 
		list = new JList(colornames);
 
		//This is how many the user can see by default.
		list.setVisibleRowCount(4);
 
		//This is so the user only can select ONE.
		list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
 
		add(new JScrollPane(list));
 
		list.addListSelectionListener(
				new ListSelectionListener(){
 
					//This is need, when we use the ListSelectionListener.
					public void valueChanged(ListSelectionEvent event) {
 
						//This will set the background color.
						getContentPane().setBackground(colors[list.getSelectedIndex()]);
					}
 
				}
				);
	}
}

Please Help me, I wanna learn Java - so please be nice to me, and explain VERY NOOB-FRENDLY what I did worng, and how I can fix it - Thank You!