*/
  private static final Collector<Object, ?, Optional<Object>> TO_OPTIONAL =
      Collector.of(
          ToOptionalState::new,
          ToOptionalState::add,
          ToOptionalState::combine,
          ToOptionalState::getOptional,
          Collector.Characteristics.UNORDERED);

  /**
   * A collector that converts a stream of zero or one elements to an {@code Optional}.
   *

      super.orderEntriesByValue(valueComparator);
      return this;
    }

    @Override
    @CanIgnoreReturnValue
    Builder<K, V> combine(ImmutableMap.Builder<K, V> builder) {
      super.combine(builder);
      return this;
    }

    /**
     * Returns a newly-created immutable bimap. The iteration order of the returned bimap is the

      for (Cell<? extends R, ? extends C, ? extends V> cell : table.cellSet()) {
        put(cell);
      }
      return this;
    }

    @CanIgnoreReturnValue
    Builder<R, C, V> combine(Builder<R, C, V> other) {
      this.cells.addAll(other.cells);
      return this;
    }

    /**
     * Returns a newly-created immutable table.
     *

  public void testToImmutableMap_java7_combine() {
    ImmutableMap.Builder<String, Integer> zis =
        ImmutableMap.<String, Integer>builder().put("one", 1);
    ImmutableMap.Builder<String, Integer> zat =
        ImmutableMap.<String, Integer>builder().put("two", 2).put("three", 3);
    assertMapEquals(zis.combine(zat).build(), "one", 1, "two", 2, "three", 3);
  }

        putAll(entry.getKey(), entry.getValue());
      }
      return this;
    }

    @CanIgnoreReturnValue
    @Override
    Builder<K, V> combine(ImmutableMultimap.Builder<K, V> other) {
      super.combine(other);
      return this;
    }

    /**
     * {@inheritDoc}
     *
     * @since 8.0
     */
    @CanIgnoreReturnValue
    @Override

      super.putAll(multimap);
      return this;
    }

    @CanIgnoreReturnValue
    @Override
    Builder<K, V> combine(ImmutableMultimap.Builder<K, V> other) {
      super.combine(other);
      return this;
    }

    /**
     * {@inheritDoc}
     *
     * @since 8.0
     */
    @CanIgnoreReturnValue
    @Override

    checkNonnegative(k, "k");
    checkNotNull(comparator);
    return Collector.of(
        () -> TopKSelector.<T>least(k, comparator),
        TopKSelector::offer,
        TopKSelector::combine,
        TopKSelector::topK,
        Collector.Characteristics.UNORDERED);
  }

  /**
   * Returns a {@code Collector} that returns the {@code k} greatest (relative to the specified

        put(entry.getKey(), entry.getValue());
      }
      return this;
    }

    @CanIgnoreReturnValue
    Builder<K, V> combine(Builder<K, V> builder) {
      entries.addAll(builder.entries);
      return this;
    }

    /**
     * Returns an {@code ImmutableRangeMap} containing the associations previously added to this
     * builder.

    public Builder<E> addAll(Iterator<? extends E> elements) {
      super.addAll(elements);
      return this;
    }

    @CanIgnoreReturnValue
    @Override
    Builder<E> combine(ImmutableSet.Builder<E> builder) {
      super.combine(builder);
      return this;
    }

    /**
     * Returns a newly-created {@code ImmutableSortedSet} based on the contents of the {@code
     * Builder} and its comparator.

    public Builder<C> addAll(Iterable<Range<C>> ranges) {
      for (Range<C> range : ranges) {
        add(range);
      }
      return this;
    }

    @CanIgnoreReturnValue
    Builder<C> combine(Builder<C> builder) {
      addAll(builder.ranges);
      return this;
    }

    /**
     * Returns an {@code ImmutableRangeSet} containing the ranges added to this builder.
     *