JMSL Tutorial: MusicJob

We present an alternative design practice to add custom functionality to a MusicJob. Instead of defining a subclass of MusicJob and overriding its repeat() method, we can use a stock MusicJob, and plug in a Playable at run time. Let's look at the Playable interface:

 public double play(double playTime, Composable thing)

Any class that satisfies the Playable interface can be added to a MusicJob's startPlayables, repeatPlayables, or stopPlayables. The "Composable thing" parameter in the play() method above will point to the parent who calls play. In this case it is our MusicJob.

You can create a Playable "on the fly" and add it to a MusicJob like this:

myMusicJob.addRepeatPlayable(new Playable() {
   public double play(double playTime, Composable thing) {
    // do something, anything
    return playTime;
   }
});

Or you can define a Playable as is shown below:

/** A Playable that prints a message */

package jmsltutorial;
import com.softsynth.jmsl.*;

public class MessagePrintingPlayable implements Playable {
String message = "uninitialized";

 MessagePrintingPlayable(String msg) {
        message = msg;
 }

 public double play(double playTime, Composable thing) {
        JMSL.out.println(message);
        return playTime;
 }

}

Here's how you would add this to your MusicJob's repeatPlayables:

myMusicJob.addRepeatPlayable(new MessagePrintingPlayable());

Next, we will instantiate a few of these MessagePrintingPlayables and add them into a MusicJob's start, repeat, and stop playables.

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  (C) 1997 Phil Burk and Nick Didkovsky, All Rights Reserved
  JMSL is based upon HMSL (C) Phil Burk, Larry Polansky and David Rosenboom.