EmptyIteratorTester() {
      super(3, MODIFIABLE, Collections.<Integer>emptySet(), IteratorTester.KnownOrder.KNOWN_ORDER);
    }
  }

  @GwtIncompatible // Only used by @GwtIncompatible code
  private abstract static class SingletonIteratorTester extends IteratorTester<Integer> {
    SingletonIteratorTester() {
      super(3, MODIFIABLE, singleton(1), IteratorTester.KnownOrder.KNOWN_ORDER);
    }
  }

   * serializable.
   *
   * <p><b>Java 8+ users and later:</b> Prefer {@link Collections#unmodifiableNavigableSet}.
   *
   * @param set the navigable set for which an unmodifiable view is to be returned
   * @return an unmodifiable view of the specified navigable set
   * @since 12.0
   */
  public static <E extends @Nullable Object> NavigableSet<E> unmodifiableNavigableSet(
      NavigableSet<E> set) {

        if (protocolsCopy != this.protocols) {
          this.routeDatabase = null
        }

        // Assign as an unmodifiable list. This is effectively immutable.
        this.protocols = protocolsCopy.unmodifiable()
      }

    /**
     * Sets the verifier used to confirm that response certificates apply to requested hostnames for
     * HTTPS connections.
     *

  }

  /**
   * Returns an unmodifiable view of the specified collection, preserving the interface for
   * instances of {@code SortedSet}, {@code Set}, {@code List} and {@code Collection}, in that order
   * of preference.
   *
   * @param collection the collection for which to return an unmodifiable view
   * @return an unmodifiable view of the collection
   */

  }

  /** Returns an unmodifiable view of {@code iterator}. */
  public static <T extends @Nullable Object> UnmodifiableIterator<T> unmodifiableIterator(
      Iterator<? extends T> iterator) {
    checkNotNull(iterator);
    if (iterator instanceof UnmodifiableIterator) {
      @SuppressWarnings("unchecked") // Since it's unmodifiable, the covariant cast is safe

import okhttp3.internal.indexOfFirstNonAsciiWhitespace
import okhttp3.internal.indexOfLastNonAsciiWhitespace
import okhttp3.internal.publicsuffix.PublicSuffixDatabase
import okhttp3.internal.toCanonicalHost
import okhttp3.internal.unmodifiable
import okhttp3.internal.url.FRAGMENT_ENCODE_SET
import okhttp3.internal.url.FRAGMENT_ENCODE_SET_URI
import okhttp3.internal.url.PASSWORD_ENCODE_SET
import okhttp3.internal.url.PATH_SEGMENT_ENCODE_SET

    /* No aliasing on inverse operations. */
    assertSame(unmod.inverse(), unmod.inverse());
    assertSame(unmod, unmod.inverse().inverse());

    /* Unmodifiable is a view. */
    mod.put(4, "four");
    assertEquals(true, unmod.get(4).equals("four"));
    assertEquals(true, unmod.inverse().get("four").equals(4));

    /* No aliasing on inverse operations. */
    assertSame(unmod.inverse(), unmod.inverse());
    assertSame(unmod, unmod.inverse().inverse());

    /* Unmodifiable is a view. */
    mod.put(4, "four");
    assertEquals(true, unmod.get(4).equals("four"));
    assertEquals(true, unmod.inverse().get("four").equals(4));