import java.applet.AudioClip;
import java.net.URL;

public class MyApplet
   {

   // sound clip to make a frog ribbet croaking sound
   private AudioClip frog;

   /**
     * Get the applet started.
     */
   public void init()
      {
      // You must initialise frog in init, not the usual static or instance initialiser,
      // ribbet.au is a sound file in the jar under the same package as the Applet
      // The file must be an au, wav, midi or aiff.
      // BEWARE getResource only works in Applets signed with a real certificate.
      URL u = MyApplet.class.getResource( "ribbet.au" );
      if ( u == null )
         {
         throw new IllegalArgumentException ( "ribbet.au missing from the jar" );
         }
      if ( DEBUGGING )
         {
         // see where Java is getting your resource
         out.println( u );
         }
      frog = getAudioClip( u );
      ...
      }
   ...

   public void croak()
      {
      // make the sound
      frog.play();
      }
   }