*  /   \ /   \
   * c     d     e
   *        \   /
   *         \ /
   *          f
   * }</pre>
   *
   * <p><b>Note on binary trees</b>
   *
   * <p>This method can be used to traverse over a binary tree. Given methods {@code
   * leftChild(node)} and {@code rightChild(node)}, this method can be called as
   *
   * <pre>{@code
   * Traverser.forTree(node -> ImmutableList.of(leftChild(node), rightChild(node)));

        hasher.putString("The quick brown fox jumps over the lazy dog", UTF_8).hash().toString());
    assertThrows(IllegalStateException.class, () -> hasher.putInt(42));
  }

  public void testHashTwice() {
    Hasher hasher = Hashing.hmacMd5(MD5_KEY).newHasher();

    assertEquals(
        "9753980fe94daa8ecaa82216519393a9",
        hasher.putString("The quick brown fox jumps over the lazy dog", UTF_8).hash().toString());

  static final Iterable<Integer> ALL_INTEGER_CANDIDATES;

  static {
    ImmutableSet.Builder<Integer> intValues = ImmutableSet.builder();
    // Add boundary values manually to avoid over/under flow (this covers 2^N for 0 and 31).
    intValues.add(Integer.MAX_VALUE - 1, Integer.MAX_VALUE);
    // Add values up to 40. This covers cases like "square of a prime" and such.
    for (int i = 1; i <= 40; i++) {

    } catch (UnsupportedOperationException expected) {
    }
  }

  /**
   * Verifies that an Iterator is unmodifiable.
   *
   * <p>This test only works with iterators that iterate over a finite set.
   */
  public static void assertIteratorIsUnmodifiable(Iterator<?> iterator) {
    while (iterator.hasNext()) {
      iterator.next();
      try {
        iterator.remove();

 * Generally speaking, this class reduces object allocation and memory consumption at the price of
 * moderately increased constant factors of CPU. Only use this class when there is a specific reason
 * to prioritize memory over CPU.
 *
 * @author Dimitris Andreou
 * @author Jon Noack
 */
@GwtIncompatible // not worth using in GWT for now
@ElementTypesAreNonnullByDefault

   * convenient.
   *
   * <p>By default, a {@code Builder} will generate bimaps that iterate over entries in the order
   * they were inserted into the builder. For example, in the above example, {@code
   * WORD_TO_INT.entrySet()} is guaranteed to iterate over the entries in the order {@code "one"=1,
   * "two"=2, "three"=3}, and {@code keySet()} and {@code values()} respect the same order. If you

        return null;
      }
      // Successfully crossed over from min to max.
      // Bubble up max levels.
      E parent;
      // If toTrickle is moved up to a parent of removeIndex, the parent is
      // placed in removeIndex position. We must return that to the iterator so
      // that it knows to skip it.
      if (crossOver < removeIndex) {
        // We crossed over to the parent level in crossOver, so the parent

      backingMap.remove(element);
    }

    frequency.add(-numberRemoved);
    size -= numberRemoved;
    return oldCount;
  }

  // Roughly a 33% performance improvement over AbstractMultiset.setCount().
  @CanIgnoreReturnValue
  @Override
  public int setCount(@ParametricNullness E element, int count) {
    checkNonnegative(count, "count");

    Count existingCounter;

 * A sorted set of contiguous values in a given {@link DiscreteDomain}. Example:
 *
 * <pre>{@code
 * ContiguousSet.create(Range.closed(5, 42), DiscreteDomain.integers())
 * }</pre>
 *
 * <p>Note that because bounded ranges over {@code int} and {@code long} values are so common, this
 * particular example can be written as just:
 *
 * <pre>{@code
 * ContiguousSet.closed(5, 42)
 * }</pre>
 *

   * specified is included. To create a copy of a {@code SortedSet} that preserves the comparator,
   * call {@link #copyOfSorted} instead. This method iterates over {@code elements} at most once.
   *
   * <p>Note that if {@code s} is a {@code Set<String>}, then {@code ImmutableSortedSet.copyOf(s)}
   * returns an {@code ImmutableSortedSet<String>} containing each of the strings in {@code s},