}
  }

  /*
   * Preconditions.checkNotNull is *intended* for performing eager null checks on parameters that a
   * nullness checker can already "prove" are non-null. That means that the first parameter to
   * checkNotNull *should* be annotated to require it to be non-null.
   *
   * However, for a variety of reasons, Google developers have written a ton of code over the past

    node.thread = null; // mark as 'deleted'
    restart:
    while (true) {
      Waiter pred = null;
      Waiter curr = waiters;
      if (curr == Waiter.TOMBSTONE) {
        return; // give up if someone is calling complete
      }
      Waiter succ;
      while (curr != null) {
        succ = curr.next;
        if (curr.thread != null) { // we aren't unlinking this node, update pred.

    List<@Nullable String> list = newArrayList("a", null, "b", null, "a", null);
    assertEquals(2, Iterators.frequency(list.iterator(), "a"));
    assertEquals(1, Iterators.frequency(list.iterator(), "b"));
    assertEquals(0, Iterators.frequency(list.iterator(), "c"));
    assertEquals(0, Iterators.frequency(list.iterator(), 4.2));
    assertEquals(3, Iterators.frequency(list.iterator(), null));
  }

  @GwtIncompatible // slow (~4s)

    TreeSet<Integer> set = Sets.newTreeSet(SOME_COLLECTION);
    verifySortedSetContents(set, SOME_COLLECTION, null);
  }

  public void testNewTreeSetFromIterable() {
    TreeSet<Integer> set = Sets.newTreeSet(SOME_ITERABLE);
    verifySortedSetContents(set, SOME_ITERABLE, null);
  }

  public void testNewTreeSetFromIterableDerived() {

   *
   * @throws NullPointerException if any key or value in {@code map} is null
   */
  @SuppressWarnings("unchecked")
  public static <K, V> ImmutableSortedMap<K, V> copyOfSorted(SortedMap<K, ? extends V> map) {
    Comparator<? super K> comparator = map.comparator();
    if (comparator == null) {
      // If map has a null comparator, the keys should have a natural ordering,

    WeakReference<Object> ref = new WeakReference<>(null);
    int expectedComputations = 0;
    for (int i = 0; i < iterations; i++) {
      // The entry should get garbage collected and recomputed.
      Object oldValue = ref.get();
      if (oldValue == null) {
        expectedComputations++;
      }
      ref = new WeakReference<>(cache.getUnchecked(1));
      oldValue = null;
      Thread.sleep(i);
      System.gc();

    }
  }

  /*
   * Preconditions.checkNotNull is *intended* for performing eager null checks on parameters that a
   * nullness checker can already "prove" are non-null. That means that the first parameter to
   * checkNotNull *should* be annotated to require it to be non-null.
   *
   * However, for a variety of reasons, Google developers have written a ton of code over the past

   * constructor uses a null {@code Comparator} to mean "natural ordering," whereas this factory
   * rejects null. Clean your code accordingly.
   *
   * @param comparator the comparator to use to sort the set
   * @return a new, empty {@code TreeSet}
   * @throws NullPointerException if {@code comparator} is null
   */
  public static <E extends @Nullable Object> TreeSet<E> newTreeSet(

    }
    if (keyStrength != null) {
      s.add("keyStrength", Ascii.toLowerCase(keyStrength.toString()));
    }
    if (valueStrength != null) {
      s.add("valueStrength", Ascii.toLowerCase(valueStrength.toString()));
    }
    if (keyEquivalence != null) {
      s.addValue("keyEquivalence");
    }
    if (valueEquivalence != null) {
      s.addValue("valueEquivalence");
    }

      synchronized (mutex) {
        Collection<V> collection = super.get(key);
        return (collection == null) ? null : typePreservingCollection(collection, mutex);
      }
    }

    @Override
    public Set<Map.Entry<K, Collection<V>>> entrySet() {
      synchronized (mutex) {
        if (asMapEntrySet == null) {
          asMapEntrySet = new SynchronizedAsMapEntries<>(delegate().entrySet(), mutex);
        }