*  Fix: Don't miss whole operation timeouts when calls redirect.
 *  Fix: Don't leak connections if web sockets have malformed responses or if `onOpen()` throws.
 *  Fix: Don't retry when request bodies fail due to `FileNotFoundException`.
 *  Fix: Don't crash when URLs have IPv4-mapped IPv6 addresses.
 *  Fix: Don't crash when building `HandshakeCertificates` on Android API 28.

@GwtCompatible
public final class Futures extends GwtFuturesCatchingSpecialization {

  // A note on memory visibility.
  // Many of the utilities in this class (transform, withFallback, withTimeout, asList, combine)
  // have two requirements that significantly complicate their design.
  // 1. Cancellation should propagate from the returned future to the input future(s).
  // 2. The returned futures shouldn't unnecessarily 'pin' their inputs after completion.

 *
 * A URL has several components.
 *
 * ### Scheme
 *
 * Sometimes referred to as *protocol*, A URL's scheme describes what mechanism should be used to
 * retrieve the resource. Although URLs have many schemes (`mailto`, `file`, `ftp`), this class only
 * supports `http` and `https`. Use [java.net.URI][URI] for URLs with arbitrary schemes.
 *
 * ### Username and Password
 *

 * href="https://github.com/ben-manes/caffeine/wiki">Caffeine</a>. Its API is designed to make it a
 * nearly drop-in replacement. Note that it is not available for Android or GWT/J2CL and that it may
 * have <a href="https://github.com/ben-manes/caffeine/wiki/Guava">different (usually better)
 * behavior</a> when multiple threads attempt concurrent mutations. Its equivalent to {@code
 * CacheBuilder} is its <a

    taskFaker.runNextTask()
    assertThat(cache.remove("a")).isTrue()
    assertAbsent("a")
    cache.close()
    createNewCache()

    // The journal will have no record that 'a' was removed. It will have an entry for 'a', but when
    // it tries to read the cache files, it will find they were deleted. Once it encounters an entry
    // with missing cache files, it should remove it from the cache entirely.

   * number of elements and every element of {@code iterator1} is equal to the corresponding element
   * of {@code iterator2}.
   *
   * <p>Note that this will modify the supplied iterators, since they will have been advanced some
   * number of elements forward.
   */
  public static boolean elementsEqual(Iterator<?> iterator1, Iterator<?> iterator2) {
    while (iterator1.hasNext()) {
      if (!iterator2.hasNext()) {

   * predicate. The returned multimap is a live view of {@code unfiltered}; changes to one affect
   * the other.
   *
   * <p>The resulting multimap's views have iterators that don't support {@code remove()}, but all
   * other methods are supported by the multimap and its views. When adding a key that doesn't

   * predicate. The returned multimap is a live view of {@code unfiltered}; changes to one affect
   * the other.
   *
   * <p>The resulting multimap's views have iterators that don't support {@code remove()}, but all
   * other methods are supported by the multimap and its views. When adding a key that doesn't

    /**
     * Returns an immutable copy of the current contents of this set view. Does not support null
     * elements.
     *
     * <p><b>Warning:</b> this may have unexpected results if a backing set of this view uses a
     * nonstandard notion of equivalence, for example if it is a {@link TreeSet} using a comparator
     * that is inconsistent with {@link Object#equals(Object)}.
     */

 * them, even though they usually won't be needed. If you have such arguments, use the conventional
 * if/throw idiom instead.
 *
 * <p>Depending on your message arguments, memory may be allocated for boxing and varargs array
 * creation. However, the methods of this class have a large number of overloads that prevent such
 * allocations in many common cases.
 *