* @since 2.0
 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public final class Sets {
  private Sets() {}

  /**
   * {@link AbstractSet} substitute without the potentially-quadratic {@code removeAll}
   * implementation.
   */
  abstract static class ImprovedAbstractSet<E extends @Nullable Object> extends AbstractSet<E> {
    @Override
    public boolean removeAll(Collection<?> c) {

    }
    for (int j = 0; j < 1000; j++) {
      builder.add(9);
    }
    ImmutableSortedSet<Integer> unused = builder.build();
    assertThat(compares[0]).isAtMost(10000);
    // hopefully something quadratic would have more digits
  }

  public static <E extends @Nullable Object> CopyOnWriteArrayList<E> newCopyOnWriteArrayList(
      Iterable<? extends E> elements) {
    // We copy elements to an ArrayList first, rather than incurring the
    // quadratic cost of adding them to the COWAL directly.
    Collection<? extends E> elementsCollection =
        (elements instanceof Collection)
            ? (Collection<? extends E>) elements
            : newArrayList(elements);

      InCompletionOrderState<T> localState = state;
      if (localState != null) {
        // Don't print the actual array! We don't want inCompletionOrder(list).toString() to have
        // quadratic output.
        return "inputCount=["
            + localState.inputFutures.length
            + "], remaining=["
            + localState.incompleteOutputCount.get()
            + "]";
      }

      InCompletionOrderState<T> localState = state;
      if (localState != null) {
        // Don't print the actual array! We don't want inCompletionOrder(list).toString() to have
        // quadratic output.
        return "inputCount=["
            + localState.inputFutures.length
            + "], remaining=["
            + localState.incompleteOutputCount.get()
            + "]";
      }