}

    @Override
    public @Nullable V replace(K key, V value) {
      throw new UnsupportedOperationException();
    }

    @Override
    public V computeIfAbsent(
        K key, java.util.function.Function<? super K, ? extends V> mappingFunction) {
      throw new UnsupportedOperationException();
    }

    @Override
    public @Nullable V computeIfPresent(

    checkNotNull(key);
    checkNotNull(function);
    int hash = hash(key);
    return segmentFor(hash).compute(key, hash, function);
  }

  @Override
  public V computeIfAbsent(K key, Function<? super K, ? extends V> function) {
    checkNotNull(key);
    checkNotNull(function);
    return compute(key, (k, oldValue) -> (oldValue == null) ? function.apply(key) : oldValue);
  }