Declaring Variables In GUIs

In most of the GUI examples, it declares the variables right at the start as private.

public class KiloConverterWindow extends JFrame
{
private JPanel panel;
private JLabel messageLabel;
private JTextField kiloTextField;
private JButton calcButton;
private final int WINDOW_WIDTH = 310;
private final int WINDOW_HEIGHT = 100;

In one example though, it declares and creates the different objects in the constructor.

public BorderWindow()
{
setTitle("Border Layout");
setSize(WINDOW_WIDTH, WINDOW_HEIGHT);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new BorderLayout());

JButton button1 = new JButton("North Button");
JButton button2 = new JButton("South Button");
JButton button3 = new JButton("East Button");
JButton button4 = new JButton("West Button");
JButton button5 = new JButton("Center Button");

Now what I assume, is that for the second example snippet, because it's sole purpose is to show you the Border layout, there are no events tied to any buttons, and there is no data, other than the names of the buttons. With the first snippet, it's purpose was to show the kilometer to miles converter using a GUI. The purpose of making it private is to prevent the data from being altered from outside code. If I have the right idea, I feel like they should have continued to keep their examples consistent.