code: public static byte[] readFileAtOnce(final String filename) throws IOException {
  		final FileInputStream fIn = new FileInputStream(filename);
  		return readFileAtOnce(fIn);
  	}
docs: Reads the contents of the file at once and returns the byte array.
  
  @param filename
  name of the file.
  @throws java.io.IOException if any.
  @return an array of byte.