Moving Star Java Method #1

package com.zetcode.main;

import java.awt.EventQueue;
import javax.swing.JFrame;

@SuppressWarnings("serial")
public class Zetcode extends JFrame
{

    public Zetcode()
    {

        add(new Board());

        setTitle("Star");

        setResizable(false);
        pack();
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public static void main(String[] args)
    {
        EventQueue.invokeLater(new Runnable()
        {

            @Override
            public void run()
            {
                JFrame ex = new Zetcode();
                ex.setVisible(true);
            }
        });
    }
}
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/* In the Board class we animate a star that will move from the
 * upper left corner to the bottom right corner.
 */
package com.zetcode.main;

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.ImageIcon;
import javax.swing.JPanel;
import javax.swing.Timer;

@SuppressWarnings("serial")
public class Board extends JPanel implements ActionListener
{

	/* Four constants are defined. The first two constants are the board width and height.
	 * The third and fourth are the initial coordinates of the star.
	 * The last one determines the speed of the animation.
	 */
    private final int B_WIDTH = 350;
    private final int B_HEIGHT = 350;
    private final int INITIAL_X = -40;
    private final int INITIAL_Y = -40;
    private final int DELAY = 25;

    private Image star;
    private Timer timer;
    private int x, y;

    public Board()
    {

        loadImage();
        initBoard();
    }

    /* In the loadImage() method we create an instance of the
     * ImageIcon class. The image is located in the project
     * directory. The getImage() method will return the the Image
     * object from this class. This object will be drawn on the
     * board.
     */
    private void loadImage()
    {

        ImageIcon ii = new ImageIcon("star.png");
        star = ii.getImage();
    }

    private void initBoard()
    {

        setBackground(Color.BLACK);
        setPreferredSize(new Dimension(B_WIDTH, B_HEIGHT));

        /* Our JPanel component will use a buffer to paint. This
         * means that all drawing will be done in memory first.
         * Later the off-screen buffer will be copied to the
         * screen. In this simple example, we might not notice
         * any differences.
         */
        setDoubleBuffered(true);

        x = INITIAL_X;
        y = INITIAL_Y;

        /* Here we create a Swing Timer class and call its start()
         * method. Every DELAY ms the timer will call the
         * actionPerformed() method. In order to use the
         * actionPerformed() method, we must implement the
         * ActionListener interface.
         */
        timer = new Timer(DELAY, this);
        timer.start();
    }

    /* Custom painting is done in the paintComponent() method in
     * Swing. Note that we also call the paintComponent() method
     * of the parent (JPanel). The actual painting is delegated
     * to the drawStar() method.
     */
    @Override
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);

        drawStar(g);
    }

    /* In the drawStar() method, we draw the image on the window
     * with the usage of the drawImage() method.
     */
    private void drawStar(Graphics g)
    {
        Graphics2D g2d = (Graphics2D) g;
        g2d.drawImage(star, x, y, this);
        /* We must synchronize the painting on Linux systems.
         * Otherwise, the animation would not be smooth.
         */
        Toolkit.getDefaultToolkit().sync();
        g.dispose();
    }

    /* In the actionPerformed() method we increase the x, y values
     * of the star object. Then we call the repaint() method,
     * which will cause the paintComponent() to be called. This
     * way we regularly repaint the Board thus making the
     * animation.
     */
    @Override
    public void actionPerformed(ActionEvent e)
    {

        x += 1;
        y += 1;

        if (y > B_HEIGHT) {

            y = INITIAL_Y;
            x = INITIAL_X;
        }

        repaint();
    }
}