My Bouncing Ball

import java.awt.Graphics;
import java.awt.Color;

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

import javax.swing.JFrame;
import javax.swing.JComponent;
import javax.swing.Timer;

class BouncingBall extends JComponent implements ActionListener {

    private int x = 0;
    private int y = 0;
    private int size = 50;

    private int horizontalStep = 1;
    private int verticalStep = 1;

    private int delay = 2;

    private Color color = Color.BLUE;

    private BouncingBall() {

        // set canvas to an initial size,
        // otherwise it won't show up
        this.setSize(1, 1);

        // create timer to redraw the circle
        // after the delay time has expired
        Timer timer = new Timer(delay, this);

        // start the timer
        timer.start();
    }

    public void actionPerformed(ActionEvent e) {

        // boundaries
        int west = 0;
        int south = this.getHeight() - 1 - size;
        int east = this.getWidth() - 1 - size;
        int north = 0;

        // increment step for x coordinate,
        // check for boundaries and invert
        // direction if necessary
        this.x = this.x + this.horizontalStep;
        if (this.x < west || this.x > east) {
            this.horizontalStep = this.horizontalStep * -1;
            this.x = this.x + 2 * this.horizontalStep;
        }

        // dito for y coordinate
        this.y = this.y + this.verticalStep;
        if (this.y < north || this.y > south) {
            this.verticalStep = this.verticalStep * -1;
            this.y = this.y + 2 * this.verticalStep;
        }

        // fancy gimmick for changing the color
        // when the circle hits a boundary
        if (this.x == west || this.x == east || this.y == north || this.y == south) {
            this.color = color.equals(Color.BLUE) ? Color.RED : Color.BLUE;
        }

        // call for repainting the canvas
        this.repaint();
    }

    @Override
    public void paintComponent(Graphics g) {

        // fit canvas size to window size
        this.setSize(this.getParent().getSize());

        // fill background
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, this.getWidth(), this.getHeight());

        // draw circle shape
        g.setColor(this.color);
        g.fillOval(x, y, size, size);
    }

    public static void main(String[] args) {

        JFrame window = new JFrame("My Bouncing Ball");
        window.setLocation(100, 100);
        window.setSize(800, 600);
        window.getContentPane().add(new BouncingBall());
        window.setVisible(true);
    }

}