Velocity Reviews - A question about some long java code that has getters/setters

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A question about some long java code that has getters/setters

The following code, which is taken from one of my school books,
displays 4 different boxes inside a gui

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

public class TestMessagePanel extends JFrame {

public TestMessagePanel() {
MessagePanel messagePanel1 = new MessagePanel("Top Left");
MessagePanel messagePanel2 = new MessagePanel("Top Right");
MessagePanel messagePanel3 = new MessagePanel("Bottom Left");
MessagePanel messagePanel4 = new MessagePanel("Bottom Right");
messagePanel1.setBackground(Color.RED);
messagePanel2.setBackground(Color.CYAN);
messagePanel3.setBackground(Color.GREEN);
messagePanel4.setBackground(Color.WHITE);
messagePanel1.setCentered(true);

setLayout(new GridLayout(2, 2));
add(messagePanel1);
add(messagePanel2);
add(messagePanel3);
add(messagePanel4);
}

public static void main(String[] args) {
TestMessagePanel frame = new TestMessagePanel();
frame.setSize(300, 200);
frame.setTitle("TestMessagePanel");
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOS E);
frame.setVisible(true);

}//end main()
}

class MessagePanel extends JPanel {

private String message = "Nope";
private int xCoordinate = 20;
private int yCoordinate = 20;
private int interval = 10;
private boolean centered;

public MessagePanel() {
}

public MessagePanel(String message) {
this.message = message;
}

public String getMessage() {
return message;
}

public void setMessage(String message) {
this.message = message;
repaint();
}

public int getXCoordinate() {
return xCoordinate;
}

public void setXCoordinate(int x) {
this.xCoordinate = x;
repaint();
}

public int getYCoordinate() {
return yCoordinate;
}

public void setYCoordinate(int y) {
this.xCoordinate = y;
repaint();
}

public boolean isCentered() {
return centered;
}

public void setCentered(boolean centered) {
this.centered = centered;
repaint();
}

public int getInterval() {
return interval;
}

public void setInterval(int interval) {
this.interval = interval;
repaint();
}

protected void paintComponent(Graphics g) {
super.paintComponent(g);

if (centered) {
FontMetrics fm = g.getFontMetrics();
int stringWidth = fm.stringWidth(message);
int stringAscent = fm.getAscent();
xCoordinate = getWidth() / 2 - stringWidth / 2;
yCoordinate = getWidth() / 2 - stringAscent / 2;
}
g.drawString(message, xCoordinate, yCoordinate);
}

public void MoveLeft() {
xCoordinate -= interval;
repaint();
}

public void MoveRight() {
xCoordinate += interval;
repaint();
}

public void moveUp() {
yCoordinate -= interval;
repaint();
}

public void moveDown() {
yCoordinate += interval;
repaint();
}

public Dimension getPreferredSize() {
return new Dimension(200, 30);
}
}

What I don't get is why the book defines stuff like getXCoordinate(),
getYCoordinate(), and getInterval() when it doesn't even use them in
this very long code example. I tried reading over the section in the
book, but the author gives no explanation on why he included a bunch
of unused getters/setters. On top of that, the code seems to work fine
when I comment out these methods.

Ideas?

Chad