code: public static boolean isZero(byte[] bytes) {
  		int x = 0;
  		for (int i = 0; i < bytes.length; i++) {
  			x |= bytes[i];
  		}
  		return x == 0;
  	}
docs: Checks whether a byte array just contains elements equal to zero
  @param  bytes input byte array
  @return true if all bytes of the array are 0