* state: BLOCKED, WAITING, or TIMED_WAITING.
   */
  void waitForThreadToEnterWaitState(Thread thread, long timeoutMillis) {
    long startTime = System.nanoTime();
    for (; ; ) {
      Thread.State s = thread.getState();
      if (s == Thread.State.BLOCKED || s == Thread.State.WAITING || s == Thread.State.TIMED_WAITING)
        return;

      }
    }

    void awaitWaiting() {
      while (!isBlocked()) {
        if (getState() == State.TERMINATED) {
          throw new RuntimeException("Thread exited");
        }
        Thread.yield();
      }
    }

    private boolean isBlocked() {
      return getState() == Thread.State.WAITING && LockSupport.getBlocker(this) == future;
    }
  }

    // NPE on null listener, so we propagate that contract up into the add method as well.
    checkNotNull(runnable, "Runnable was null.");
    checkNotNull(executor, "Executor was null.");

    // Lock while we check state. We must maintain the lock while adding the new pair so that
    // another thread can't run the list out from under us. We only add to the list if we have not
    // yet started execution.
    synchronized (this) {

  /**
   * This field encodes the current state of the future.
   *
   * <p>The valid values are:
   *
   * <ul>
   *   <li>{@code null} initial state, nothing has happened.
   *   <li>{@link Cancellation} terminal state, {@code cancel} was called.
   *   <li>{@link Failure} terminal state, {@code setException} was called.
   *   <li>{@link SetFuture} intermediate state, {@code setFuture} was called.

  }

  private static void assertIntact(MinMaxPriorityQueue<?> q) {
    if (!q.isIntact()) {
      fail("State " + Arrays.toString(q.toArray()));
    }
  }

  private static void assertIntactUsingSeed(long seed, MinMaxPriorityQueue<?> q) {
    if (!q.isIntact()) {
      fail("Using seed " + seed + ". State " + Arrays.toString(q.toArray()));
    }
  }

  private static void assertIntactUsingStartedWith(

     * StackOverflowError: We can't reliably call setException(error).
     *
     * - Any kind of Error from a listener. Even if we could distinguish that case (by exposing some
     * extra state from AbstractFuture), our options are limited: A call to setException() would be
     * a no-op. We could log, but if that's what we really want, we should modify

     * iterator's next element and pass it to the reference iterator through this method so it can
     * return the same element. This enables the assertion to pass and the reference iterator to
     * properly update its state.
     */
    void promoteToNext(E e) {
      if (nextElements.remove(e)) {
        nextElements.push(e);
      } else {
        throw new UnknownElementException(nextElements, e);
      }
    }

   *         .build();
   * }</pre>
   *
   * <p>Elements appear in the resulting set in the same order they were first added to the builder.
   *
   * <p>Building does not change the state of the builder, so it is still possible to add more
   * elements and to build again.
   *
   * @since 2.0
   */
  public static class Builder<E> extends ImmutableCollection.Builder<E> {
    /*

   * containing two inner lists of three and two elements, all in the original order.
   *
   * <p>The outer list is unmodifiable, but reflects the latest state of the source list. The inner
   * lists are sublist views of the original list, produced on demand using {@link List#subList(int,
   * int)}, and are subject to all the usual caveats about modification as explained in that API.

     * It will require more memory but will reduce indirection.
     */

    /*
     * Segments maintain a table of entry lists that are ALWAYS kept in a consistent state, so can
     * be read without locking. Next fields of nodes are immutable (final). All list additions are
     * performed at the front of each bin. This makes it easy to check changes, and also fast to