}
      };
    }

    @Override
    public NavigableSet<E> elementSet() {
      return new StandardElementSet();
    }

    @Override
    public Entry<E> firstEntry() {
      return standardFirstEntry();
    }

    @Override
    public Entry<E> lastEntry() {
      return standardLastEntry();
    }

    @Override
    public Entry<E> pollFirstEntry() {
      return standardPollFirstEntry();

        }
      };
    }

    @Override
    public NavigableSet<E> elementSet() {
      return new StandardElementSet();
    }

    @Override
    public Entry<E> firstEntry() {
      return standardFirstEntry();
    }

    @Override
    public Entry<E> lastEntry() {
      return standardLastEntry();
    }

    @Override
    public Entry<E> pollFirstEntry() {
      return standardPollFirstEntry();

   *
   * <p>If you override {@link #entrySet()}, you may wish to override {@link #firstEntry()} to
   * forward to this implementation.
   */
  protected @Nullable Entry<E> standardFirstEntry() {
    Iterator<Entry<E>> entryIterator = entrySet().iterator();
    if (!entryIterator.hasNext()) {
      return null;
    }
    Entry<E> entry = entryIterator.next();

   *
   * <p>If you override {@link #entrySet()}, you may wish to override {@link #firstEntry()} to
   * forward to this implementation.
   */
  protected @Nullable Entry<E> standardFirstEntry() {
    Iterator<Entry<E>> entryIterator = entrySet().iterator();
    if (!entryIterator.hasNext()) {
      return null;
    }
    Entry<E> entry = entryIterator.next();

    }

    @Override
    public @Nullable K higherKey(K key) {
      return standardHigherKey(key);
    }

    @Override
    public @Nullable Entry<K, V> firstEntry() {
      return standardFirstEntry();
    }

    /*
     * We can't override lastEntry to delegate to standardLastEntry, as it would create an infinite
     * loop. Instead, we test standardLastEntry manually below.
     */

    }

    @Override
    public @Nullable K higherKey(K key) {
      return standardHigherKey(key);
    }

    @Override
    public @Nullable Entry<K, V> firstEntry() {
      return standardFirstEntry();
    }

    /*
     * We can't override lastEntry to delegate to standardLastEntry, as it would create an infinite
     * loop. Instead, we test standardLastEntry manually below.
     */

   *
   * <p>If you override {@link #entrySet()}, you may wish to override {@link #firstEntry()} to
   * forward to this implementation.
   */
  protected @Nullable Entry<E> standardFirstEntry() {
    Iterator<Entry<E>> entryIterator = entrySet().iterator();
    if (!entryIterator.hasNext()) {
      return null;
    }
    Entry<E> entry = entryIterator.next();

   * #entrySet}. If you override {@code entrySet}, you may wish to override {@code firstEntry} to
   * forward to this implementation.
   */
  protected @Nullable Entry<K, V> standardFirstEntry() {
    return Iterables.<@Nullable Entry<K, V>>getFirst(entrySet(), null);
  }

  /**
   * A sensible definition of {@link #firstKey} in terms of {@code firstEntry}. If you override

   * #entrySet}. If you override {@code entrySet}, you may wish to override {@code firstEntry} to
   * forward to this implementation.
   */
  protected @Nullable Entry<K, V> standardFirstEntry() {
    return Iterables.<@Nullable Entry<K, V>>getFirst(entrySet(), null);
  }

  /**
   * A sensible definition of {@link #firstKey} in terms of {@code firstEntry}. If you override