Meter changes in Java MIDI

Question

I am writing a program that creates a midi file as output. This midifile can then be loaded into a sequencer and viewed as music notation.
The problem is that would like to know how to implement a meter change (ie time signature)
Can someone send me an example of some code that does this? I've ready the Sun java reference page extensively as well as many many other web pages, and all stop short of this topic.
Thanks

Answer 1

Here's the code I ended up using for creating and reading tempo change and time signature change messages. Note that Java doesn't support unsigned bytes, so when reading the value you have to check the sign before converting to int. Also, I haven't tested this with any outside equipment, just my own software synth.
code:
    final int TEMPO_MESSAGE = 0x51;
    MetaMessage tempoChangeMessage(int bpm) // bpm==beats per minute
         long mpq=60000000 / bpm; // mpq==microsec per quarter (beat)
         byte[] data = new byte[3];
         data[0] = (byte)((mpq >> 16) & 0xFF);
         data[1] = (byte)((mpq >> 8) & 0xFF);
         data[2] = (byte)(mpq & 0xFF);
         MetaMessage m = new MetaMessage();
         try
              m.setMessage(TEMPO_MESSAGE, data, data.length);
         catch (InvalidMidiDataException e)
         return m;
    boolean isTempoChangeMessage(MidiMessage m)
         if (!(m instanceof MetaMessage))
              return false;
         return ((MetaMessage)m).getType() == TEMPO_MESSAGE;
    // returns beats (quarter notes) per minute
    int getTempoFromMessage(MetaMessage m)
         byte[] byteData = m.getData();
         int[] intData = new int[3];
         // fix for lack of unsigned byte type
         for (int i=0 ; i<3 ; ++i)
              if (byteData[i] < 0)
                   intData[i] = byteData[i] + 256;
              else
                   intData[i] = byteData;
     long mpq=(intData[0] << 16) + (intData[1] << 8) + (intData[2]);
     return (mpq == 0 ? 1 : (int)(60000000 / mpq));
// denominator = 2 ^ denominatorExponent, eg 6, 3 gives 6/8 time
final int TIME_SIGNATURE_MESSAGE = 0x58;
MetaMessage timeSignatureChangeMessage(int numerator, int denominatorExponent)
     byte[] data = new byte[4];
     data[0] = (new Integer(numerator)).byteValue();
     data[1] = (new Integer(denominatorExponent)).byteValue();
     data[2] = (new Integer(24)).byteValue(); // ignoring this
     data[3] = (new Integer(8)).byteValue(); // ignoring this
     MetaMessage m = new MetaMessage();
     try
          m.setMessage(TIME_SIGNATURE_MESSAGE, data, data.length);
     catch (InvalidMidiDataException e)
          // oh well...
     return m;
boolean isTimeSignatureChangeMessage(MidiMessage m)
     if (!(m instanceof MetaMessage))
          return false;
     return ((MetaMessage)m).getType() == TIME_SIGNATURE_MESSAGE;      
// returns numerator, assume 1/4 notes so ignore denominator exponent etc
int getTimeSignatureFromMessage(MetaMessage m)
     byte[] data = m.getData();
     return data[0];
int quarterNotesPerBar=getTimeSignatureFromMessage(m);