}

  private enum Algorithm {
    MD5("MD5", Hashing.md5()),
    SHA_1("SHA-1", Hashing.sha1()),
    SHA_256("SHA-256", Hashing.sha256()),
    SHA_384("SHA-384", Hashing.sha384()),
    SHA_512("SHA-512", Hashing.sha512());

    private final String algorithmName;
    private final HashFunction hashFn;

    Algorithm(String algorithmName, HashFunction hashFn) {
      this.algorithmName = algorithmName;

  }

  /** Returns a hash function implementing the SHA-512 algorithm (512 hash bits). */
  public static HashFunction sha512() {
    return Sha512Holder.SHA_512;
  }

  private static final class Sha512Holder {
    static final HashFunction SHA_512 =
        new MessageDigestHashFunction("SHA-512", "Hashing.sha512()");
  }

  /**