Head First Java P346 - MiniMusic Apps - hanging and not returning to the command line

[marten kay]

A quick question, I think.

I am running the MiniMusicCmdApp class below - it compiles and almost functions as expected, except after it makes the sound the class hangs (blinking cursor - see image), and I have to close down Command Prompt, reset my path etc when I reopen it.

Is this a bad class, or is there something wrong with my computer settings?

Thanks

Marten

import javax.sound.midi.*;
 
public class MiniMusicCmdLine { // this is the first one
 
public static void main(String[] args) {
MiniMusicCmdLine mini = new MiniMusicCmdLine();
if (args.length <2 ) {
System.out.println("Don't forget the instrument and not 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();
b.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

EDIT by mw: Added Code Tags.
[ February 24, 2007: Message edited by: marc weber ]

[David McCombs]

I am not sure why it is hanging, but you can use cntl-c to force the program to shut down. Check the books website to see if there is a known problem in the code.

Sorry I couldn't be more helpful.
[ February 24, 2007: Message edited by: David McCombs ]

[marten kay]

but you can use cntl-c to for the program to shut down

Thanks David, while it does not solve the problem, it does help a lot.

Marten

[marc weber]

At the end of the try block (immediately after calling player.start();), try adding the following...

Thread.sleep(2000);
player.close();
System.exit(0);

This will cause a 2-second pause (which should be long enough for the player to play the note you specified), after which it will close the Sequencer and exit the program.
[ February 25, 2007: Message edited by: marc weber ]

[marten kay]

Thanks Marc, this did the trick and I am one step further on the OO journey. Not sure why they did not include in the book... probably did not want to confuse the message...