Minim FFT returning zero for some files

Hello,

I'm writing a program which takes the FFT of various files in a folder and then writes the FFT data to a text file for a machine learning algorithim. However, for many of the files I process, I get zero out for all bands causing me to lose lots of potential data.

I'm also getting the error of "JavaSound Minim Error: Error Reading from File - Stream Closed" on many of the files, though I'm not sure if it affects the FFT data.

Here's my code (I'm new to coding so I'm open to pointers on my code too):

import ddf.minim.analysis.*;
import ddf.minim.*;
import java.io.*;

Minim       minim;
AudioPlayer player;
FFT         fft;
FileWriter fw;

int counter = 0;

void setup()
{

 minim = new Minim(this);

 try
 {

     //create .txt file to record data
     fw = new FileWriter("audioRawData.txt");
     //run data() which reads .wav files and outputs FFT data to text file
    data();


 }

 catch (IOException e)
 {

 }

}


 void data()
{

  try
  {

  //list files in a directory given by filePath
  String filePath = "";
  File[] files = new File(filePath).listFiles();

  //loop thru files
  for(File file : files)
  {
   //get name of file
   String fileName = file.getName();

   //only process if .wav file
   if (fileName.contains(".wav"))
   {

     //counter to keep track
     counter = counter + 1 ;

     //print counter and file name to keep track of what's being processed
     println(counter);
     println(fileName);

     //load file in Minim and play using AudioPlayer
     player = minim.loadFile(filePath + fileName);
     player.play();

     //create new FFT and use Hamming window
     fft = new FFT(player.bufferSize(), player.sampleRate());
     fft.window(FFT.HAMMING);

     //some files might be stereo, so use mix channel
     fft.forward(player.mix);

     //since all files in the directory are true, write 1 before the FFT data
     fw.write("1 ");

     //go through FFT using loop
     for(int i = 0; i < fft.specSize(); i++)

      {
         //write FFT with band number in front of it, convert to dB
         fw.write((i + 1) + ":" + 20 * log( 2 * fft.getBand(i) / fft.timeSize() ) + " ");

     }

       //create new line to start next file data on
       fw.write("\n");
       //close the player to avoid running out of memory
       player.close();

  }


  }




  //close and flush writer when done
  print("Done Writing!");
  fw.close();
  fw.flush();

 }



catch (IOException e)
{

}

//terminate program when done
exit();
}