Convert.java

import java.awt.Desktop;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.List;

import javax.swing.JOptionPane;
import javax.swing.JProgressBar;
import javax.swing.SwingWorker;

public class Convert extends SwingWorker<Void, Integer> {
  File input;
  File output;
  JProgressBar bar;

  String midiHeader = "4D54686400000006000000010060";
  String mtrk = "4D54726B";
  String ende = "FF2F00";
  int count;

  public Convert(JProgressBar bar, File input, File output) {
    this.input = input;
    this.output = output;
    this.bar = bar;
    bar.setIndeterminate(true);
  }
  
  @Override
  protected Void doInBackground() throws Exception {
    // *** Read Input ***
    StringBuilder sbHex = new StringBuilder();

    try {
      int value = 0;
      int i = 0;
      InputStream is = new FileInputStream(input);
      while ((value = is.read()) != -1) {
        i++;
        publish(i);
        sbHex.append(String.format("%02X", value));
      }
      is.close();
    } catch (IOException e) {
    }

    // *** Analyze Input ***

    String hexaBup = sbHex.toString();
    count = 0;
    for (int a = 0; a < (hexaBup.length() - mtrk.length()); a++) {
      if (hexaBup.substring(a, mtrk.length() + a).equals(mtrk)) {
        count++;
        String midi = midiHeader + hexaBup.substring(a, hexaBup.indexOf(ende, a) + 6);
        
        // *** Save Output ***
        
        int len = midi.length();
        byte[] data = new byte[len / 2];
        for (int i = 0; i < len; i += 2) {
          data[i / 2] = (byte) ((Character.digit(midi.charAt(i), 16) << 4) + Character.digit(midi.charAt(i + 1), 16));
        }
        
        try {
          OutputStream os = new FileOutputStream(new File(output.getPath() + "_" + String.valueOf(count) + ".mid"));
          os.write(data);
          os.close();
        } catch (IOException e) {}
      }
    }

    try {
      Desktop.getDesktop().open(output.getParentFile());
    } catch (IOException e) {}
    return null;
  }
  
  @Override
  protected void done() {
    bar.setIndeterminate(false);
    bar.setString("Converted Midi: " + String.valueOf(count));

    if (count == 0) {
      JOptionPane.showMessageDialog(null, "Could not extract any midi file!", "No midi file found",
          JOptionPane.ERROR_MESSAGE);
    }
  }

  @Override
  protected void process(List<Integer> chunks) {
    int i = chunks.get(chunks.size() - 1);
    bar.setString(String.valueOf(i) + " data sets");
  }
}