});
          // requireNonNull is safe because the first `size` elements have been filled in.
          Entry<K, V> firstEntry = requireNonNull(entryArray[0]);
          K prevKey = firstEntry.getKey();
          keys[0] = prevKey;
          values[0] = firstEntry.getValue();
          checkEntryNotNull(keys[0], values[0]);
          for (int i = 1; i < size; i++) {

              });
          // requireNonNull is safe because the first `size` elements have been filled in.
          Entry<K, V> firstEntry = requireNonNull(entryArray[0]);
          K prevKey = firstEntry.getKey();
          keys[0] = prevKey;
          values[0] = firstEntry.getValue();
          checkEntryNotNull(keys[0], values[0]);
          for (int i = 1; i < size; i++) {

        }
        return descendingMap;
      }
    }

    @Override
    @CheckForNull
    public Map.Entry<K, V> firstEntry() {
      synchronized (mutex) {
        return nullableSynchronizedEntry(delegate().firstEntry(), mutex);
      }
    }

    @Override
    @CheckForNull
    public Map.Entry<K, V> floorEntry(K key) {
      synchronized (mutex) {

        }
        return descendingMap;
      }
    }

    @Override
    @CheckForNull
    public Map.Entry<K, V> firstEntry() {
      synchronized (mutex) {
        return nullableSynchronizedEntry(delegate().firstEntry(), mutex);
      }
    }

    @Override
    @CheckForNull
    public Map.Entry<K, V> floorEntry(K key) {
      synchronized (mutex) {