}
  }

  /**
   * SetBuilderImpl version that uses a JDK HashSet, which has built in hash flooding protection.
   */
  private static final class JdkBackedSetBuilderImpl<E> extends SetBuilderImpl<E> {
    private final Set<Object> delegate;

    JdkBackedSetBuilderImpl(SetBuilderImpl<E> toCopy) {
      super(toCopy); // initializes dedupedElements and distinct
      delegate = Sets.newHashSetWithExpectedSize(distinct);