package headfirst.combined.djview;  import javax.sound.midi.*;import java.util.*;public class BeatModel implements BeatModelInterface, MetaEventListener {    Sequencer sequencer;	ArrayList beatObservers = new ArrayList();	ArrayList bpmObservers = new ArrayList();    int bpm = 90;    Sequence sequence;    Track track; 	public void initialize() {        setUpMidi();        buildTrackAndStart();	}     public void on() {        sequencer.start();        setBPM(90);    }     public void off() {		setBPM(0);		sequencer.stop();    }     public void setBPM(int bpm) {		this.bpm = bpm;		sequencer.setTempoInBPM(getBPM());		notifyBPMObservers();    }  	public int getBPM() {		return bpm;	}  	void beatEvent() {		notifyBeatObservers();	}     	public void registerObserver(BeatObserver o) {		beatObservers.add(o);	}  	public void notifyBeatObservers() {		for(int i = 0; i < beatObservers.size(); i++) {			BeatObserver observer = (BeatObserver)beatObservers.get(i);			observer.updateBeat();		}	}  	public void registerObserver(BPMObserver o) {		bpmObservers.add(o);	}  	public void notifyBPMObservers() {		for(int i = 0; i < bpmObservers.size(); i++) {			BPMObserver observer = (BPMObserver)bpmObservers.get(i);			observer.updateBPM();		}	}	public void removeObserver(BeatObserver o) {		int i = beatObservers.indexOf(o);		if (i >= 0) {			beatObservers.remove(i);		}	}	public void removeObserver(BPMObserver o) {		int i = bpmObservers.indexOf(o);		if (i >= 0) {			bpmObservers.remove(i);		}	}    public void meta(MetaMessage message) {        if (message.getType() == 47) {			beatEvent();        	sequencer.start();        	setBPM(getBPM());        }    }	public void setUpMidi() {		try {			sequencer = MidiSystem.getSequencer();			sequencer.open();			sequencer.addMetaEventListener(this);			sequence = new Sequence(Sequence.PPQ,4);			track = sequence.createTrack();			sequencer.setTempoInBPM(getBPM());		} catch(Exception e) {				e.printStackTrace();		}    }      public void buildTrackAndStart() {        int[] trackList = {35, 0, 46, 0};            sequence.deleteTrack(null);        track = sequence.createTrack();      	makeTracks(trackList);		track.add(makeEvent(192,9,1,0,4));      	 	try {			sequencer.setSequence(sequence);                    		} catch(Exception e) {			e.printStackTrace();		}    }                 public void makeTracks(int[] list) {                      for (int i = 0; i < list.length; i++) {          int key = list[i];          if (key != 0) {             track.add(makeEvent(144,9,key, 100, i));             track.add(makeEvent(128,9,key, 100, i+1));          }       }    }            public  MidiEvent makeEvent(int comd, int chan, int one, int two, int tick) {        MidiEvent event = null;        try {            ShortMessage a = new ShortMessage();            a.setMessage(comd, chan, one, two);            event = new MidiEvent(a, tick);                    } catch(Exception e) {			e.printStackTrace(); 		}        return event;    }}