* is the only one in use, but if we encounter nested concatenations, we start a deque of
     * meta-iterators rather than letting the nesting get arbitrarily deep.  This keeps each
     * operation O(1).
     */

    private @Nullable Iterator<? extends Iterator<? extends T>> topMetaIterator;

    // Only becomes nonnull if we encounter nested concatenations.

   *
   * @throws ParameterNotInstantiableException if the static methods cannot be invoked because the
   *     default value of a parameter cannot be determined.
   * @throws IllegalAccessException if the class isn't public or is nested inside a non-public
   *     class, preventing its methods from being accessible.
   * @throws InvocationTargetException if a static method threw exception.
   */

 * Benchmarks (as of December 2011) show that:
 *
 * <ul>
 *   <li>for an unnested {@code lock()} and {@code unlock()}, a cycle detecting lock takes 38ns as
 *       opposed to the 24ns taken by a plain lock.
 *   <li>for nested locking, the cost increases with the depth of the nesting:
 *       <ul>
 *         <li>2 levels: average of 64ns per lock()/unlock()
 *         <li>3 levels: average of 77ns per lock()/unlock()

    Object writeReplace() {
    return super.writeReplace();
  }

  // This class is never actually serialized directly, but we have to make the
  // warning go away (and suppressing would suppress for all nested classes too)
  @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;

 *   <li>Static methods named {@code copyOf} (or {@code copyOfSorted}), accepting an existing
 *       collection whose contents should be copied.
 *   <li>A static nested {@code Builder} class which can be used to populate a new immutable
 *       instance.
 * </ul>
 *
 * <h4>Warnings</h4>
 *
 * <ul>

            <includes>
              <include>${test.include}</include>
            </includes>
            <!-- By having our own entries here, we also override the default exclusion filter, which excludes all nested classes. -->
            <excludes>
              <!-- https://github.com/google/guava/issues/2840 -->
              <exclude>%regex[.*PackageSanityTests.*.class]</exclude>

 *   <li>Static methods named {@code copyOf} (or {@code copyOfSorted}), accepting an existing
 *       collection whose contents should be copied.
 *   <li>A static nested {@code Builder} class which can be used to populate a new immutable
 *       instance.
 * </ul>
 *
 * <h4>Warnings</h4>
 *
 * <ul>

            <includes>
              <include>${test.include}</include>
            </includes>
            <!-- By having our own entries here, we also override the default exclusion filter, which excludes all nested classes. -->
            <excludes>
              <!-- https://github.com/google/guava/issues/2840 -->
              <exclude>%regex[.*PackageSanityTests.*.class]</exclude>

                sb.append("]");
            }
            sb.append("; ");
            target = target.getCause();
            if (target != null) {
                sb.append("nested: ");
            }
        }
        return sb.toString();
    }

    /**
     * Processes a label request.
     * @param request The HTTP request.
     * @param response The HTTP response.

  }

  /*
   * @IgnoreJRERequirement should be redundant with the one on Streams itself, but it's necessary as
   * of Animal Sniffer 1.24. Maybe Animal Sniffer processes this nested class before it processes
   * Streams and thus hasn't had a chance to see Streams's annotation?
   */
  @IgnoreJRERequirement
  private abstract static class MapWithIndexSpliterator<
          F extends Spliterator<?>,