Head First Java chapter 11 MiniMiniMusicApp

[Rob Gman]

I'm getting a rather nasty error at runtime when trying to get this very simple sound player to work, I get the same error with the code I typed out and the pre-written code that comes with the book :-/ so i guess there is nothing wrong with the code? Here is it

   
package chap11;
 
import javax.sound.midi.*;
 

 

 
public class MiniMiniMusicApp {   // this is the first one
 
       
 
     public static void main(String[] args) {
 
        MiniMiniMusicApp mini = new MiniMiniMusicApp();
 
        mini.play();
 
     }
 

 
    public void play() {
 

 
      try {
 

 
         // make (and open) a sequencer, make a sequence and track
 

 
         Sequencer sequencer = MidiSystem.getSequencer();         
 
         sequencer.open();
 
        
 
         Sequence seq = new Sequence(Sequence.PPQ, 4);
 
         Track track = seq.createTrack();     
 

 
         // now make two midi events (containing a midi message)
 
         MidiEvent event = null;
 
         
 
         // first make the message
 
         // then stick the message into a midi event 
 
         // and add the event to the track
 

 
          ShortMessage a = new ShortMessage();
 
          a.setMessage(144, 1, 44, 100);
 
          MidiEvent noteOn = new MidiEvent(a, 1); // <-- means at tick one, the above event happens
 
          track.add(noteOn);
 

 
          ShortMessage b = new ShortMessage();
 
          b.setMessage(128, 1, 44, 100);
 
          MidiEvent noteOff = new MidiEvent(b, 16); // <-- means at tick one, the above event happens
 
          track.add(noteOff);
 
        
 
         // add the events to the track
 
            
 
          // add the sequence to the sequencer, set timing, and start
 
          sequencer.setSequence(seq);
 
         
 
          sequencer.start();
 
          // new
 
          Thread.sleep(1000);
 
          sequencer.close();
 
          System.exit(0);
 
      } catch (Exception ex) {ex.printStackTrace();}
 
  } // close play
 

 
} // close class
 

and this is the runtime error

Exception in thread "main" java.lang.UnsatisfiedLinkError: init_
at gnu.javax.sound.midi.alsa.AlsaMidiDeviceProvider.init_(libgcj.so.81)
at gnu.javax.sound.midi.alsa.AlsaMidiDeviceProvider.<clinit>(libgcj.so.81)
at java.lang.Class.initializeClass(libgcj.so.81)
at java.lang.Class.newInstance(libgcj.so.81)
at gnu.classpath.ServiceProviderLoadingAction.run(libgcj.so.81)
at java.security.AccessController.doPrivileged(libgcj.so.81)
at gnu.classpath.ServiceFactory$ServiceIterator.loadNextServiceProvider(libgcj.so.81)
at gnu.classpath.ServiceFactory$ServiceIterator.<init>(libgcj.so.81)
at gnu.classpath.ServiceFactory.lookupProviders(libgcj.so.81)
at javax.sound.midi.MidiSystem.getMidiDeviceInfo(libgcj.so.81)
at javax.sound.midi.MidiSystem.getSequencer(libgcj.so.81)
at MiniMiniMusicApp.play(MiniMiniMusicApp.java:12)
at MiniMiniMusicApp.main(MiniMiniMusicApp.java:6)

if anyone can tell me what this means i'd be very grateful

[Vijay Raj]

Look at java.lang.UnsatisfiedLinkError in API doc, it says

Thrown if the Java Virtual Machine cannot find an appropriate native-language definition of a method declared native

Vijay.

[roshni bhagat]

have you written the same code as in book or added something...because i have run the same code and it runs very well

[Campbell Ritchie]

Not quite sure what the UnsatisfiedLinkError means, but it might be worthwhile reinstalling your JDK.

[marc weber]

Since this seems to stem from a native method call, I'm also curious what operating system you're using.

[Rob Gman]

Ubuntu.... perhaps I should have mentioned that at the start?

[marc weber]

Originally posted by Rob Gman:
Ubuntu.... perhaps I should have mentioned that at the start?

Interesting. I found that AlsaMidiDeviceProvider seems to be part of open source Java sound from Tritonus.org. You might try updating/reinstalling that, or perhaps find an alternative.

[Campbell Ritchie]

I have had UnsatisfiedLinkErrors on Ubuntu 5 before now, but not on Ubuntu 6.04 or 6.10. Might still be worthwhile trying to reinstall your JDK.

[Arnout Engelen]

I ran into the same. Looks like you have 'tritonus' installed (which should give you access to ALSA MIDI though the Java Sound API), but the native library wasn't loaded.

You can load the native library with:

System.load("/usr/lib/jni/libtritonusalsa.so.1.0");

This gets rid of the linking error (but still doesn't quite seem work for me: the ALSA MIDI device shows up in qjackctl, but connecting it to kmidimon doesn't show any notes coming though).

[Rob Spoor]

"raboof",

Please read your private messages regarding an important announcement.

Thank you,

Rob

[Campbell Ritchie]

"Rob Gman" you have a similar private message; make sure to read it please.

[Atlantis Lacy]

Don't know if this is resolved but I removed the chapter 11 statement at the top of the code just before the import.

Atlantis lacy

[Campbell Ritchie]

By "removed" do you mean the package statement? Since package names are used when invoking class files with the JVM, that might make a lot of difference. There are bits in the Java Tutorials about packages, here too, which are worth reading.