I try to get the spectral flux first in an audio, but why is that every time I run my program,  the MEAN SPECTRAL FLUX changes though I am just using the same test audio file?

Also, is there a way to getBand() without playing the audio.

1. import ddf.minim.spi.*;
   import ddf.minim.signals.*;
   import ddf.minim.*;
   import ddf.minim.analysis.*;
   import ddf.minim.ugens.*;
   import ddf.minim.effects.*;
   import java.io.*;
   
   Minim minim;
   AudioPlayer input;
   FFT fft;
   String sound;
   String windowName;
   
   int index;
   
   double[] spectrum;
   double[] myspectrum;
   double[] lastspectrum;
   
   double spectralcentroid = 0;
   double spectralflux = 0;
   
   void setup()
   {
     size(512, 200, P3D);
    
     minim = new Minim(this);
     //sound = getParameter("sound");
     sound = "D:/Downloads/Brown Shrike Call 3.wav";
     input = minim.loadFile(sound);
     input.play();
    
     fft = new FFT(input.bufferSize(), input.sampleRate());
    
     myspectrum = new double[input.bufferSize()];
     spectrum = new double[fft.specSize()];
     lastspectrum = new double[fft.specSize()];
    
     Arrays.fill( lastspectrum, 0 );
   }
   
   void draw()
   {
    
     fft.forward(input.mix);
    
     /*-------------SPECTRAL FLUX---------------*/
     double flux = 0;
     for( int i = 0 ; i < fft.specSize() ; i++)
     {
        spectrum[i] = Math.abs(fft.getBand(i));
        flux += spectrum[i] - lastspectrum[i];
     }
    
     spectralflux += flux;
    
     try{
     // Create file
     FileWriter fstream = new FileWriter("features.txt");
     BufferedWriter out = new BufferedWriter(fstream);
     out.write("Bandwidth: " + Double.toString(fft.getBandWidth()));
     out.newLine();
     out.write("Spectral Flux: " + Double.toString(spectralflux/fft.specSize()));
     //Close the output stream
     out.close();
     }catch (Exception e){//Catch exception if any
     System.err.println("Error: " + e.getMessage());
     }
    
     if(input.isPlaying() == false) exit();
   }
   
   void stop()
   {
     // always close Minim audio classes when you finish with them
     input.close();
     minim.stop();
    
     super.stop();
   }