У меня есть непонимание какой вариант использовать вариант 1 
FileInputStream streamIn = new FileInputStream(fileName) ;
BufferedInputStream streamInBuf = new BufferedInputStream (streamIn, 6400) ;
byte[] byteArray = new byte[streamInBuf.available()];
streamInBuf.read(byteArray);
streamInBuf.close()
вариант 2 
FileInputStream streamIn = new FileInputStream(fileName) ;
byte[] byteArray = new byte[streamIn.available()];
streamIn.read(byteArray);
streamIn.close()
вариант 3 
FileInputStream streamIn = new FileInputStream(fileName) ;
BufferedInputStream streamInBuf = new BufferedInputStream (streamIn, 6400) ;
int c;
while((c = streamInBuf.read()) != -1)
    {}
streamInBuf.close()