code: public static void verifySavedMD5(File dataFile, MD5Hash expectedMD5)
        throws IOException {
      MD5Hash storedHash = readStoredMd5ForFile(dataFile);
      // Check the hash itself
      if (!expectedMD5.equals(storedHash)) {
        throw new IOException(
            "File " + dataFile + " did not match stored MD5 checksum " +
            " (stored: " + storedHash + ", computed: " + expectedMD5);
      }
    }
docs: Verify that the previously saved md5 for the given file matches
  expectedMd5.
  @throws IOException