code: public void saveFingerprintAsFile(byte[] fingerprint, String filename) {
  
          FileOutputStream fileOutputStream;
          try {
              fileOutputStream = new FileOutputStream(filename);
              fileOutputStream.write(fingerprint);
              fileOutputStream.close();
          } catch (IOException e) {
              e.printStackTrace();
          }
      }
docs: Save fingerprint to a file
  
  @param fingerprint	fingerprint bytes
  @param filename		fingerprint filename
  @see	FingerprintManager file saved