// already using Collections.newSetFromMap and ConcurrentHashMap.
    return Collections.newSetFromMap(new ConcurrentHashMap<E, Boolean>());
  }

  static <E> Set<E> newLinkedHashSetWithExpectedSize(int expectedSize) {
    return Sets.newLinkedHashSetWithExpectedSize(expectedSize);
  }

  /**
   * Returns the platform preferred map implementation that preserves insertion order when used only
   * for insertions.
   */

  }

  /**
   * Returns the platform preferred implementation of an insertion ordered set based on a hash
   * table.
   */
  static <E extends @Nullable Object> Set<E> newLinkedHashSetWithExpectedSize(int expectedSize) {
    return Sets.newLinkedHashSetWithExpectedSize(expectedSize);
  }

  /**
   * Returns the platform preferred map implementation that preserves insertion order when used only
   * for insertions.
   */

  }

  /**
   * Returns the platform preferred implementation of an insertion ordered set based on a hash
   * table.
   */
  static <E extends @Nullable Object> Set<E> newLinkedHashSetWithExpectedSize(int expectedSize) {
    return CompactLinkedHashSet.createWithExpectedSize(expectedSize);
  }

  /**
   * Returns the platform preferred map implementation that preserves insertion order when used only