Playing Audio in an Applet

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Applets can also play short sound clips, using the same "load once in init(), use it later" pattern you just saw for images. The type involved this time is java.applet.AudioClip, and it's about as simple as AWT-era APIs get.

Note: This page's code is a preview, not something you can run right on this website - this server runs PHP, not a Java runtime. See Environment Setup for how to actually compile and run it.

Loading a Clip: getAudioClip()

Just like getImage(), getAudioClip() takes a base URL and a filename, and is best called once inside init():

AudioClip clip = getAudioClip(getDocumentBase(), "click.wav");

The base-URL choice works exactly as covered in Displaying Images: getDocumentBase() for a file next to the HTML page, getCodeBase() for one bundled next to the compiled classes.

File formats: historically, applets played the .au format above all others, since it was supported from the very earliest JDKs. Later JDKs (before the whole API was removed) also supported more common formats like .wav and .aiff. If you're following along with an old JDK, .wav is the safest, most widely-supported choice for new examples.

The AudioClip Interface

AudioClip is refreshingly small - just three methods:

Method	Effect
`play()`	Plays the clip once, from the start
`loop()`	Plays the clip repeatedly, looping until `stop()` is called
`stop()`	Stops playback, whether it was started with `play()` or `loop()`

There's also a static convenience method, Applet.newAudioClip(URL url), which builds an AudioClip straight from a URL without needing an actual Applet instance to call it on - handy for utility code that isn't itself part of the applet.

Extending PaintApplet: A Click Sound

PaintApplet currently only listens for mouse movement, via the MouseMotionAdapter registered with addMouseMotionListener() back in Handling Mouse Events. To play a sound the moment the user presses the mouse button - starting a new stroke - we need a second, separate registration: a MouseListener (via its MouseAdapter convenience class), added with addMouseListener(). These are two different interfaces even though both are "mouse" events - one reports button presses/releases/clicks, the other reports movement/dragging.

// New field
private AudioClip clickSound;

public void init() {
    // ...existing title/bgcolor/background-image handling stays here...

    // New: load the click sound
    clickSound = getAudioClip(getDocumentBase(), "click.wav");

    // ...existing addMouseMotionListener(...) for dragging stays here...

    // New: a separate listener for the mouse press itself
    addMouseListener(new MouseAdapter() {
        public void mousePressed(MouseEvent e) {
            if (clickSound != null) {
                clickSound.play();
            }
        }
    });

    // ...existing addKeyListener(...) for color-switching stays here...
}

After this change, init() registers two separate mouse-related listeners on the same applet: addMouseMotionListener() keeps handling mouseDragged() to build up the list of drawn points, and the new addMouseListener() handles mousePressed() to fire a sound effect. AWT is happy to deliver both kinds of event to the same component independently - you're not replacing anything, just adding a second, unrelated listener alongside the first.

Next steps: With images and audio covered, the next few lessons shift to layout: how to arrange real AWT components like buttons instead of drawing everything by hand. Start with Layout Managers.

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