final SetBuilderImpl<E> combine(SetBuilderImpl<E> other) {
      SetBuilderImpl<E> result = this;
      for (int i = 0; i < other.distinct; i++) {
        /*
         * requireNonNull is safe because we ensure that the first `distinct` elements have been
         * populated.
         */
        result = result.add(requireNonNull(other.dedupedElements[i]));
      }
      return result;
    }

    }

    @CanIgnoreReturnValue
    Builder<K, V> combine(Builder<K, V> other) {
      checkNotNull(other);
      ensureCapacity(this.size + other.size);
      System.arraycopy(
          other.alternatingKeysAndValues,
          0,
          this.alternatingKeysAndValues,
          this.size * 2,
          other.size * 2);
      this.size += other.size;
      return this;
    }

               * with two implementations, one that contains causeless Cancellation instances and
               * the other of which creates new Cancellation instances each time it's called? Yet
               * another alternative is to fill in a non-null value for each of the fields no matter
               * what and to just not use it if !GENERATE_CANCELLATION_CAUSES.
               */
              : requireNonNull(

  }

  /**
   * Not supported. Use {@link #naturalOrder}, which offers better type-safety, instead. This method
   * exists only to hide {@link ImmutableMultiset#builder} from consumers of {@code
   * ImmutableSortedMultiset}.
   *
   * @throws UnsupportedOperationException always
   * @deprecated Use {@link ImmutableSortedMultiset#naturalOrder}, which offers better type-safety.
   */
  @DoNotCall("Use naturalOrder.")
  @Deprecated

  public final <T extends @Nullable Object> T[] toArray(T[] other) {
    checkNotNull(other);
    int size = size();

    if (other.length < size) {
      Object[] internal = internalArray();
      if (internal != null) {
        return Platform.copy(internal, internalArrayStart(), internalArrayEnd(), other);
      }
      other = ObjectArrays.newArray(other, size);
    } else if (other.length > size) {
      other[size] = null;
    }

  public final <T extends @Nullable Object> T[] toArray(T[] other) {
    checkNotNull(other);
    int size = size();

    if (other.length < size) {
      Object[] internal = internalArray();
      if (internal != null) {
        return Platform.copy(internal, internalArrayStart(), internalArrayEnd(), other);
      }
      other = ObjectArrays.newArray(other, size);
    } else if (other.length > size) {
      other[size] = null;
    }

    Builder<E> combine(Builder<E> other) {
      if (hashTable != null) {
        for (int i = 0; i < other.size; ++i) {
          // requireNonNull is safe because the first `size` elements are non-null.
          add((E) requireNonNull(other.contents[i]));
        }
      } else {
        addAll(other.contents, other.size);
      }
      return this;
    }

    /**

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

    @CanIgnoreReturnValue
    Builder<E> combine(Builder<E> other) {
      addAll(other.contents, other.size);
      return this;
    }

    /**
     * Returns a newly-created {@code ImmutableList} based on the contents of the {@code Builder}.
     */
    @Override

  public void testPuttingTheSameKeyTwiceThrowsOnBuild() {
    Builder<String, Integer> builder =
        new Builder<String, Integer>()
            .put("one", 1)
            .put("one", 1); // throwing on this line might be better but it's too late to change

    try {
      builder.buildOrThrow();
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testBuildKeepingLast_allowsOverwrite() {

      }
      if (object instanceof MapDifference) {
        MapDifference<?, ?> other = (MapDifference<?, ?>) object;
        return entriesOnlyOnLeft().equals(other.entriesOnlyOnLeft())
            && entriesOnlyOnRight().equals(other.entriesOnlyOnRight())
            && entriesInCommon().equals(other.entriesInCommon())
            && entriesDiffering().equals(other.entriesDiffering());
      }
      return false;
    }

    @Override