* make sure they see a consistent snapshot: If modCounts change during a traversal of segments
     * loading size or checking containsValue, then we might have an inconsistent view of state so
     * (usually) must retry.
     */
    int modCount;

    /**
     * The table is expanded when its size exceeds this threshold. (The value of this field is
     * always {@code (int) (capacity * 0.75)}.)
     */
    int threshold;

 * k). In benchmarks, this implementation performs at least as well as either implementation, and
 * degrades more gracefully for worst-case input.
 *
 * <p>The implementation does not necessarily use a <i>stable</i> sorting algorithm; when multiple
 * equivalent elements are added to it, it is undefined which will come first in the output.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
final class TopKSelector<

  /**
   * Creates a new {@code ConcurrentHashMultiset} containing the specified elements, using the
   * default initial capacity, load factor, and concurrency settings.
   *
   * <p>This implementation is highly efficient when {@code elements} is itself a {@link Multiset}.
   *
   * @param elements the elements that the multiset should contain
   */
  public static <E> ConcurrentHashMultiset<E> create(Iterable<? extends E> elements) {

  /** Table of cells. When non-null, size is a power of 2. */
  @CheckForNull transient volatile Cell[] cells;

  /**
   * Base value, used mainly when there is no contention, but also as a fallback during table
   * initialization races. Updated via CAS.
   */
  transient volatile long base;

  /** Spinlock (locked via CAS) used when resizing and/or creating Cells. */

   * then we call it in a separate thread (using pseudoTimedGet). The result is that we wait as long
   * as necessary when the method is expected to return (at the cost of hanging forever if there is
   * a bug in the class under test) but that we time out fairly promptly when the method is expected

     * e.g. hash codes adversarially designed to go into ascending table locations, which keeps
     * construction O(n) (as desired) but then can have O(n) queries later.
     *
     * <p>If this returns false, then no query can take more than O(log n).
     *
     * <p>Note that for a RegularImmutableSet with elements with truly random hash codes, contains

     *
     * - If the stack overflowed before set()/setValue() could even store the result in the output
     * Future, then a call setException() would likely also overflow.
     *
     * - If the stack overflowed after set()/setValue() stored its result, then a call to
     * setException() will be a no-op because the Future is already done.
     *

    Iterator<Integer> it = mmHeap.iterator();
    assertTrue("Iterator has reached end prematurely", it.hasNext());
    it.next();
    it.next();
    try {
      it.next();
      fail("No exception thrown when iterating past end of heap");
    } catch (NoSuchElementException expected) {
    }
  }

  public void testIteratorConcurrentModification() {
    MinMaxPriorityQueue<Integer> mmHeap = MinMaxPriorityQueue.create();

    // sanity check on construction of copyOfModifiedSet
    assertThat(wrappedSet).isEqualTo(copyOfModifiedSet);

    // setToTest should throw when it calls equals(), or equals is called on it, except for itself
    assertThat(setToTest).isEqualTo(setToTest);
    assertThrows(IllegalStateException.class, () -> setToTest.equals(wrappedSet));

    // sanity check on construction of copyOfModifiedSet
    assertThat(wrappedSet).isEqualTo(copyOfModifiedSet);

    // setToTest should throw when it calls equals(), or equals is called on it, except for itself
    assertThat(setToTest).isEqualTo(setToTest);
    assertThrows(IllegalStateException.class, () -> setToTest.equals(wrappedSet));