Midi example from Head First Java

[Eubulide Megarico]

Hi everyone,
I am reading a book called "Head First Java" by Kathy Sierra and Bert Bates. One example piece of code uses a MIDI sequencer to generate a sound.
Unfortunately it doesn't work for me, even if I tried it both on Ubuntu and Windows. When I run it I only hear either a short piano note or a kind of knock.
Changing the arguments should give a different instrument and note, but it always plays the same sound when I execute it.
I don't know anything about sound and MIDI devices, so I don't know how to fix the problem.

I give the code below.
After compiling it I execute the command with different arguments:
java MiniMusicCmdLine 102 30
java MiniMusicCmdLine 80 20
java MiniMusicCmdLine 40 70

They're supposed to produce notes of different pitch, but I always hear the same short knock or sometime a piano note (but always of the same pitch).

I welcome any help at the beginner level.

----------------------

import javax.sound.midi.*;

public class MiniMiniMusicCmdLine {

public static void main(String[] args) {
MiniMiniMusicCmdLine mini = new MiniMiniMusicCmdLine();
if (args.length < 2) {
System.out.println("Don't forget the instrument and note args");
} else {
int instrument = Integer.parseInt(args[0]);
int note = Integer.parseInt(args[1]);
mini.play(instrument,note);
}
} // close main

public void play(int instrument, int note) {
try {
Sequencer player = MidiSystem.getSequencer();
player.open();
Sequence seq = new Sequence(Sequence.PPQ, 4);
Track track = seq.createTrack();

MidiEvent event = null;

ShortMessage first = new ShortMessage();
first.setMessage(192, 1, instrument, 0);
MidiEvent changeInstrument = new MidiEvent(first, 1);
track.add(changeInstrument);

ShortMessage a = new ShortMessage();
a.setMessage(144, 1, note, 100);
MidiEvent noteOn = new MidiEvent(a, 1);
track.add(noteOn);

ShortMessage b = new ShortMessage();
a.setMessage(128, 1, note, 100);
MidiEvent noteOff = new MidiEvent(b, 16);
track.add(noteOff);

player.setSequence(seq);
player.start();
} catch (Exception ex) {ex.printStackTrace();}
} // close play

} // close class

[William P O'Sullivan]

I just copied this into Eclipse and ran it.. I get the same little "knock".

Unfortunately, I don't know very much about the sound API, but I have helped others here before with similar issues.

Do a search here for midi or sound and take a look at some of the examples and fixes.


Pat.

[Campbell Ritchie]

Welcome to the Ranch
I cannot comment because I haven’t got my copy of the book here, but it is worth comparing it very carefully to what is in the book.

[Eubulide Megarico]

Hi both,
Thank you for your reply. The advice to check carefully the code from the book was right: I made a mistake in copying it! In fact line 36 should be "b.setMessage ..." instead of "a.setMessage ...". Now it works fine.
Thank you,
Eubulide

[Campbell Ritchie]

Well done finding that error