@Override
    public void replaceAll(BiFunction<? super K, ? super V, ? extends V> function) {
      throw new UnsupportedOperationException();
    }

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

    @Override
    public boolean remove(@Nullable Object key, @Nullable Object value) {

            ValueReference<K, V> valueReference = e.getValueReference();
            V entryValue = valueReference.get();
            // replace the old LoadingValueReference if it's live, otherwise
            // perform a putIfAbsent
            if (oldValueReference == valueReference
                || (entryValue == null && valueReference != UNSET)) {
              ++modCount;
              if (oldValueReference.isActive()) {

    checkNotNull(key);
    checkNotNull(value);
    int hash = hash(key);
    return segmentFor(hash).put(key, hash, value, false);
  }

  @CanIgnoreReturnValue
  @Override
  public @Nullable V putIfAbsent(K key, V value) {
    checkNotNull(key);
    checkNotNull(value);
    int hash = hash(key);
    return segmentFor(hash).put(key, hash, value, true);
  }

  @Override