</p>

<p>
If the effects of a goroutine must be observed by another goroutine,
use a synchronization mechanism such as a lock or channel
communication to establish a relative ordering.
</p>

<h3 id="chan">Channel communication</h3>

<p>
Channel communication is the main method of synchronization
between goroutines.  Each send on a particular channel

  public boolean intersects(Range<C> otherRange) {
    int ceilingIndex =
        SortedLists.binarySearch(
            ranges,
            Range::lowerBound,
            otherRange.lowerBound,
            Ordering.natural(),
            ANY_PRESENT,
            NEXT_HIGHER);
    if (ceilingIndex < ranges.size()
        && ranges.get(ceilingIndex).isConnected(otherRange)

  public boolean intersects(Range<C> otherRange) {
    int ceilingIndex =
        SortedLists.binarySearch(
            ranges,
            Range::lowerBound,
            otherRange.lowerBound,
            Ordering.natural(),
            ANY_PRESENT,
            NEXT_HIGHER);
    if (ceilingIndex < ranges.size()
        && ranges.get(ceilingIndex).isConnected(otherRange)

 */
@GwtIncompatible
final class DescendingImmutableSortedSet<E> extends ImmutableSortedSet<E> {
  private final ImmutableSortedSet<E> forward;

  DescendingImmutableSortedSet(ImmutableSortedSet<E> forward) {
    super(Ordering.from(forward.comparator()).reverse());
    this.forward = forward;
  }

  @Override
  public boolean contains(@Nullable Object object) {
    return forward.contains(object);
  }

  @Override

 */
@GwtIncompatible
final class DescendingImmutableSortedSet<E> extends ImmutableSortedSet<E> {
  private final ImmutableSortedSet<E> forward;

  DescendingImmutableSortedSet(ImmutableSortedSet<E> forward) {
    super(Ordering.from(forward.comparator()).reverse());
    this.forward = forward;
  }

  @Override
  public boolean contains(@Nullable Object object) {
    return forward.contains(object);
  }

  @Override

    implements SortedMultiset<E> {
  private final Comparator<? super E> comparator;

  // needed for serialization
  @SuppressWarnings("unchecked")
  AbstractSortedMultiset() {
    this((Comparator) Ordering.natural());
  }

  AbstractSortedMultiset(Comparator<? super E> comparator) {
    this.comparator = checkNotNull(comparator);
  }

  @Override
  public SortedSet<E> elementSet() {

  @Nullable private transient Comparator<? super E> comparator;

  @Override
  public Comparator<? super E> comparator() {
    Comparator<? super E> result = comparator;
    if (result == null) {
      return comparator = Ordering.from(forwardMultiset().comparator()).reverse();
    }
    return result;
  }

  @Nullable private transient SortedSet<E> elementSet;

  @Override
  public SortedSet<E> elementSet() {

    implements SortedMultiset<E> {
  private final Comparator<? super E> comparator;

  // needed for serialization
  @SuppressWarnings("unchecked")
  AbstractSortedMultiset() {
    this((Comparator) Ordering.natural());
  }

  AbstractSortedMultiset(Comparator<? super E> comparator) {
    this.comparator = checkNotNull(comparator);
  }

  @Override
  public NavigableSet<E> elementSet() {

  private static final long[] zeroCumulativeCounts = {0};

  static final ImmutableSortedMultiset<?> NATURAL_EMPTY_MULTISET =
      new RegularImmutableSortedMultiset<>(Ordering.natural());

  @VisibleForTesting final transient RegularImmutableSortedSet<E> elementSet;
  private final transient long[] cumulativeCounts;
  private final transient int offset;
  private final transient int length;

  @LazyInit private transient @Nullable Comparator<? super E> comparator;

  @Override
  public Comparator<? super E> comparator() {
    Comparator<? super E> result = comparator;
    if (result == null) {
      result = Ordering.from(forwardMultiset().comparator()).reverse();
      comparator = result;
    }
    return result;
  }

  @LazyInit private transient @Nullable NavigableSet<E> elementSet;

  @Override