assertNull(MessageDigestUtil.digest("MD5", null));
        assertEquals("ea703e7aa1efda0064eaa507d9e8ab7e", MessageDigestUtil.digest("MD5", text));
        assertEquals("31f30ddbcb1bf8446576f0e64aa4c88a9f055e3c", MessageDigestUtil.digest("SHA-1", text));
        assertEquals("ecb666d778725ec97307044d642bf4d160aabb76f56c0069c71ea25b1e926825", MessageDigestUtil.digest("SHA-256", text));

        try {

  }

  @CollectionSize.Require(SEVERAL)
  public void testHigherHole() {
    resetWithHole();
    assertEquals(c, navigableSet.higher(a));
    assertEquals(c, navigableSet.higher(b));
    assertEquals(null, navigableSet.higher(c));
  }

  /*
   * TODO(cpovirk): make "too small" and "too large" elements available for better navigation

  }

  /** Hasher that updates a message digest. */
  private static final class MessageDigestHasher extends AbstractByteHasher {
    private final MessageDigest digest;
    private final int bytes;
    private boolean done;

    private MessageDigestHasher(MessageDigest digest, int bytes) {
      this.digest = digest;
      this.bytes = bytes;
    }

    @Override

      throws NoSuchAlgorithmException {
    MessageDigest digest = MessageDigest.getInstance(algorithmName);
    assertEquals(
        HashCode.fromBytes(digest.digest(input)), ALGORITHMS.get(algorithmName).hashBytes(input));
    for (int bytes = 4; bytes <= digest.getDigestLength(); bytes++) {
      assertEquals(
          HashCode.fromBytes(Arrays.copyOf(digest.digest(input), bytes)),

  }

  @CollectionSize.Require(SEVERAL)
  public void testHigherHole() {
    resetWithHole();
    assertEquals(c, navigableSet.higher(a));
    assertEquals(c, navigableSet.higher(b));
    assertEquals(null, navigableSet.higher(c));
  }

  /*
   * TODO(cpovirk): make "too small" and "too large" elements available for better navigation

      throws NoSuchAlgorithmException {
    MessageDigest digest = MessageDigest.getInstance(algorithmName);
    assertEquals(
        HashCode.fromBytes(digest.digest(input)), ALGORITHMS.get(algorithmName).hashBytes(input));
    for (int bytes = 4; bytes <= digest.getDigestLength(); bytes++) {
      assertEquals(
          HashCode.fromBytes(Arrays.copyOf(digest.digest(input), bytes)),

        } catch (final UnsupportedEncodingException e) {
            throw new ClIllegalStateException(e);
        }
        final byte[] digest = msgDigest.digest();

        final StringBuilder buffer = new StringBuilder(200);
        for (final byte element : digest) {
            final String tmp = Integer.toHexString(element & 0xff);
            if (tmp.length() == 1) {
                buffer.append('0').append(tmp);

      return emptySet(comparator());
    }
  }

  @Nullable E higher(E e) {
    checkNotNull(e);
    Iterator<E> iterator = tailSet(e).iterator();
    while (iterator.hasNext()) {
      E higher = iterator.next();
      if (comparator().compare(e, higher) < 0) {
        return higher;
      }
    }
    return null;
  }

  public @Nullable E ceiling(E e) {

  }

  @Override
  public @Nullable E higher(@ParametricNullness E e) {
    return delegate().higher(e);
  }

  /**
   * A sensible definition of {@link #higher} in terms of the {@code iterator} method of {@link
   * #tailSet(Object, boolean)}. If you override {@link #tailSet(Object, boolean)}, you may wish to
   * override {@link #higher} to forward to this implementation.
   */

  }

  @Override
  public @Nullable E lower(E element) {
    return forward.higher(element);
  }

  @Override
  public @Nullable E floor(E element) {
    return forward.ceiling(element);
  }

  @Override
  public @Nullable E ceiling(E element) {
    return forward.floor(element);
  }

  @Override
  public @Nullable E higher(E element) {
    return forward.lower(element);
  }

  @Override