Lớp JScrollBar trong Java Swing

public class JScrollBar
   extends JComponent
      implements Adjustable, Accessible

package vn.viettuts.swing;

import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.AdjustmentEvent;
import java.awt.event.AdjustmentListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollBar;

public class JScrollBarExam1 {

    private JFrame mainFrame;
    private JLabel headerLabel;
    private JLabel statusLabel;
    private JPanel controlPanel;

    public JScrollBarExam1() {
        prepareGUI();
    }

    public static void main(String[] args) {
        JScrollBarExam1 demo = new JScrollBarExam1();
        demo.showScrollbarDemo();
    }

    private void prepareGUI() {
        mainFrame = new JFrame("Vi du Java Swing");
        mainFrame.setSize(400, 400);
        mainFrame.setLayout(new GridLayout(3, 1));
        mainFrame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent windowEvent) {
                System.exit(0);
            }
        });
        headerLabel = new JLabel("", JLabel.CENTER);
        statusLabel = new JLabel("", JLabel.CENTER);
        statusLabel.setSize(350, 100);
        controlPanel = new JPanel();
        controlPanel.setLayout(new FlowLayout());
        mainFrame.add(headerLabel);
        mainFrame.add(controlPanel);
        mainFrame.add(statusLabel);
        mainFrame.setVisible(true);
    }

    private void showScrollbarDemo() {
        headerLabel.setText("Control in action: JScrollbar");
        final JScrollBar horizontalScroller = new JScrollBar(JScrollBar.HORIZONTAL);
        final JScrollBar verticalScroller = new JScrollBar();
        verticalScroller.setOrientation(JScrollBar.VERTICAL);
        horizontalScroller.setMaximum(150);
        horizontalScroller.setMinimum(1);
        verticalScroller.setMaximum(150);
        verticalScroller.setMinimum(1);
        horizontalScroller.addAdjustmentListener(new AdjustmentListener() {
            @Override
            public void adjustmentValueChanged(AdjustmentEvent e) {
                statusLabel.setText(
                        "Horozontal: " + horizontalScroller.getValue() + 
                        " ,Vertical: " + verticalScroller.getValue());
            }
        });
        verticalScroller.addAdjustmentListener(new AdjustmentListener() {
            @Override
            public void adjustmentValueChanged(AdjustmentEvent e) {
                statusLabel.setText(
                        "Horozontal: " + horizontalScroller.getValue() + 
                        " ,Vertical: " + verticalScroller.getValue());
            }
        });
        controlPanel.add(horizontalScroller);
        controlPanel.add(verticalScroller);
        mainFrame.setVisible(true);
    }
}