} catch (ClassCastException e) {
      return false;
    }
  }

  @Override
  public boolean containsAll(Collection<?> targets) {
    // TODO(jlevy): For optimal performance, use a binary search when
    // targets.size() < size() / log(size())
    // TODO(kevinb): see if we can share code with OrderedIterator after it
    // graduates from labs.
    if (targets instanceof Multiset) {

    return delegateCollection().comparator();
  }

  // Override indexOf() and lastIndexOf() to be O(log N) instead of O(N).

  @GwtIncompatible // ImmutableSortedSet.indexOf
  // TODO(cpovirk): consider manual binary search under GWT to preserve O(log N) lookup
  @Override
  public int indexOf(@CheckForNull Object target) {
    int index = delegateCollection().indexOf(target);