* natural ordering.
   *
   * <p><b>Note:</b> if mutability is not required, use {@link ImmutableSortedSet#copyOf(Iterable)}
   * instead.
   *
   * <p><b>Note:</b> If {@code elements} is a {@code SortedSet} with an explicit comparator, this
   * method has different behavior than {@link TreeSet#TreeSet(SortedSet)}, which returns a {@code
   * TreeSet} with that comparator.
   *

      return new ImmutableSortedMap<>(
          ImmutableSortedSet.emptySet(comparator), ImmutableList.<V>of());
    }
  }

  /**
   * Returns the empty sorted map.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */
  @SuppressWarnings("unchecked")
  // unsafe, comparator() returns a comparator on the specified type

    protected DoubletonIteratorTester() {
      super(5, MODIFIABLE, newArrayList(1, 2), IteratorTester.KnownOrder.KNOWN_ORDER);
    }
  }

  private static Iterator<Integer> iterateOver(int... values) {
    // Note: Ints.asList's iterator does not support remove which we need for testing.
    return new ArrayList<>(Ints.asList(values)).iterator();
  }

  public void testElementsEqual() {
    Iterable<?> a;
    Iterable<?> b;

 *
 * <p>{@code Preconditions} uses {@link Strings#lenientFormat} to format error message template
 * strings. This only supports the {@code "%s"} specifier, not the full range of {@link
 * java.util.Formatter} specifiers. However, note that if the number of arguments does not match the
 * number of occurrences of {@code "%s"} in the format string, {@code Preconditions} will still

    Preconditions.checkNotNull(callback);
    future.addListener(new CallbackListener<V>(future, callback), executor);
  }

  /** See {@link #addCallback(ListenableFuture, FutureCallback, Executor)} for behavioral notes. */
  private static final class CallbackListener<V extends @Nullable Object> implements Runnable {
    final Future<V> future;
    final FutureCallback<? super V> callback;

/**
 * This class contains static utility methods that operate on or return objects of type {@link
 * Iterator}. Except as noted, each method has a corresponding {@link Iterable}-based method in the
 * {@link Iterables} class.
 *
 * <p><i>Performance notes:</i> Unless otherwise noted, all of the iterators produced in this class
 * are <i>lazy</i>, which means that they only advance the backing iteration when absolutely
 * necessary.

        thread = null;
        LockSupport.unpark(w);
      }
    }
  }

  /**
   * Marks the given node as 'deleted' (null waiter) and then scans the list to unlink all deleted
   * nodes. This is an O(n) operation in the common case (and O(n^2) in the worst), but we are saved
   * by two things.
   *
   * <ul>
   *   <li>This is only called when a waiting thread times out or is interrupted. Both of which

      return new ImmutableSortedMap<>(
          ImmutableSortedSet.emptySet(comparator), ImmutableList.<V>of());
    }
  }

  /**
   * Returns the empty sorted map.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */
  @SuppressWarnings("unchecked")
  // unsafe, comparator() returns a comparator on the specified type

   * won't cause a rehash.
   *
   * <p>As of jdk7u40, HashMap has an empty-map optimization. The argument to new HashMap(int) is
   * noted, but the initial table is a zero-length array.
   *
   * <p>This test may fail miserably on non-OpenJDK environments...
   */
  @J2ktIncompatible
  @GwtIncompatible // reflection

   * won't cause a rehash.
   *
   * <p>As of jdk7u40, HashMap has an empty-map optimization. The argument to new HashMap(int) is
   * noted, but the initial table is a zero-length array.
   *
   * <p>This test may fail miserably on non-OpenJDK environments...
   */
  @J2ktIncompatible
  @GwtIncompatible // reflection