this.existPrePage = existPrePage;
    }

    /**
     * Check if the next page exists.
     * @return true if the next page exists.
     */
    public boolean isExistNextPage() {
        return existNextPage;
    }

    /**
     * Set if the next page exists.
     * @param existNextPage true if the next page exists.
     */
    public void setExistNextPage(final boolean existNextPage) {

    }

    /**
     * Checks if there is a next page.
     * @return True if a next page exists, false otherwise.
     */
    public boolean isExistNextPage() {
        return existNextPage;
    }

    /**
     * Sets the existence of a next page.
     * @param existNextPage True if a next page exists.
     */
    public void setExistNextPage(final boolean existNextPage) {

        this.existPrePage = existPrePage;
    }

    /**
     * Checks if next page exists.
     *
     * @return true if next page exists
     */
    public boolean isExistNextPage() {
        return existNextPage;
    }

    /**
     * Sets whether next page exists.
     *
     * @param existNextPage true if next page exists
     */
    public void setExistNextPage(final boolean existNextPage) {

        this.existPrePage = existPrePage;
    }

    /**
     * Checks if a next page exists.
     * @return true if a next page exists, false otherwise.
     */
    public boolean isExistNextPage() {
        return existNextPage;
    }

    /**
     * Sets whether a next page exists.
     * @param existNextPage true if a next page exists, false otherwise.
     */

    }

    /**
     * Checks if a next page exists.
     *
     * @return true if a next page exists, false otherwise.
     */
    public boolean isExistNextPage() {
        return existNextPage;
    }

    /**
     * Sets the flag for the existence of a next page.
     *
     * @param existNextPage true if a next page exists.
     */

   * remain. This method is invoked during each call to {@link #next()} in order to compute the
   * result of a <i>future</i> call to {@code next()}.
   */
  protected abstract @Nullable T computeNext(T previous);

  @Override
  public final boolean hasNext() {
    return nextOrNull != null;
  }

  @Override
  public final T next() {
    if (nextOrNull == null) {
      throw new NoSuchElementException();

   */
  public abstract @Nullable C previous(C value);

  /**
   * Returns a signed value indicating how many nested invocations of {@link #next} (if positive) or
   * {@link #previous} (if negative) are needed to reach {@code end} starting from {@code start}.
   * For example, if {@code end = next(next(next(start)))}, then {@code distance(start, end) == 3}
   * and {@code distance(end, start) == -3}. As well, {@code distance(a, a)} is always zero.
   *

        final Indexed<String> indexed1 = it.next();
        assertThat(indexed1.getIndex(), is(0));
        assertThat(indexed1.getElement(), is("aaa"));

        final Indexed<String> indexed2 = it.next();
        assertThat(indexed2.getIndex(), is(1));
        assertThat(indexed2.getElement(), is("bbb"));

        final Indexed<String> indexed3 = it.next();
        assertThat(indexed3.getIndex(), is(2));

  private val connectionUser: ConnectionUser,
  private val fastFallback: Boolean,
) {
  // State for negotiating the next proxy to use.
  private var proxies = emptyList<Proxy>()
  private var nextProxyIndex: Int = 0

  // State for negotiating the next socket address to use.
  private var inetSocketAddresses = emptyList<InetSocketAddress>()

  // State for negotiating failed routes

        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is(sameClass(Integer.class)));

        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is(sameClass(Number.class)));

        assertThat(it.hasNext(), is(true));
        assertThat(it.next(), is(sameClass(Object.class)));

        assertThat(it.hasNext(), is(not(true)));
    }

    /**