@MapFeature.Require({SUPPORTS_PUT, SUPPORTS_REMOVE})
  public void testCompute_absentToPresent() {
    assertEquals(
        "Map.compute(absent, functionReturningValue) should return value",
        v3(),
        getMap()
            .compute(
                k3(),
                (k, v) -> {
                  assertEquals(k3(), k);
                  assertNull(v);
                  return v3();

  @MapFeature.Require({SUPPORTS_PUT, SUPPORTS_REMOVE})
  public void testCompute_absentToPresent() {
    assertEquals(
        "Map.compute(absent, functionReturningValue) should return value",
        v3(),
        getMap()
            .compute(
                k3(),
                (k, v) -> {
                  assertEquals(k3(), k);
                  assertNull(v);
                  return v3();

  void pollAndAdd(int reps) {
    for (int i = 0; i < reps; i++) {
      // TODO(kevinb): precompute random #s?
      queue.add(queue.poll() ^ random.nextInt());
    }
  }

  @Benchmark
  void populate(int reps) {
    for (int i = 0; i < reps; i++) {
      queue.clear();
      for (int j = 0; j < size; j++) {
        // TODO(kevinb): precompute random #s?
        queue.add(random.nextInt());
      }
    }
  }

  /**

    // b/80241237

    Cache<String, String> c = CacheBuilder.newBuilder().maximumSize(1).build();

    assertThat(c.asMap().compute("hash-1", (k, v) -> "a")).isEqualTo("a");
    assertThat(c.asMap().compute("hash-1", (k, v) -> "b")).isEqualTo("b");
    assertThat(c.asMap().compute("hash-1", (k, v) -> "c")).isEqualTo("c");
    assertThat(c.size()).isEqualTo(1);
    assertThat(c.asMap().computeIfAbsent("hash-2", k -> "")).isEqualTo("");

/**
 * @author Jesse Wilson
 */
final class Platform {
  static CharMatcher precomputeCharMatcher(CharMatcher matcher) {
    // CharMatcher.precomputed() produces CharMatchers that are maybe a little
    // faster (and that's debatable), but definitely more memory-hungry. We're
    // choosing to turn .precomputed() into a no-op in GWT, because it doesn't
    // seem to be a worthwhile tradeoff in a browser.
    return matcher;
  }

internal fun <T : Any> AtomicReference<Tags>.computeIfAbsent(
  type: KClass<T>,
  compute: () -> T,
): T {
  var computed: T? = null

  while (true) {
    val tags = get()

    // If the element is already present. Return it.
    val existing = tags[type]
    if (existing != null) return existing

    if (computed == null) {
      computed = compute()
    }

    assertEquals(0x388ee898bad75cbfL, hasher.hash().asLong());
  }

  /** Convenience method to compute a fingerprint on a full bytes array. */
  private static long fingerprint(byte[] bytes) {
    return fingerprint(bytes, bytes.length);
  }

  /** Convenience method to compute a fingerprint on a subset of a byte array. */
  private static long fingerprint(byte[] bytes, int length) {

        // use original key
        return parent.computeIfPresent(key, remappingFunction);
    }

    @Override
    public V compute(final K key, final BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
        // use original key
        return parent.compute(key, remappingFunction);
    }

    @Override

    assertEquals(0xcf54171253fdc198L, hasher.hash().asLong());
  }

  /** Convenience method to compute a fingerprint on a full bytes array. */
  private static long fingerprint(byte[] bytes) {
    return fingerprint(bytes, bytes.length);
  }

  /** Convenience method to compute a fingerprint on a subset of a byte array. */
  private static long fingerprint(byte[] bytes, int length) {

    this.nextOrNull = firstOrNull;
  }

  /**
   * Returns the element that follows {@code previous}, or returns {@code null} if no elements
   * remain. This method is invoked during each call to {@link #next()} in order to compute the
   * result of a <i>future</i> call to {@code next()}.
   */
  protected abstract @Nullable T computeNext(T previous);

  @Override
  public final boolean hasNext() {
    return nextOrNull != null;
  }