durationInNanos(refreshDuration, refreshTimeUnit),
            durationInNanos(that.refreshDuration, that.refreshTimeUnit));
  }

  /**
   * Converts an expiration duration/unit pair into a single Long for hashing and equality. Uses
   * nanos to match CacheBuilder implementation.
   */
  @CheckForNull
  private static Long durationInNanos(long duration, @CheckForNull TimeUnit unit) {

      do {
        stack = head;
        if (stack == null) {
          // If head == null then execute() has been called so we should just return
          return;
        }
        // try to swap null into head.
      } while (!UNSAFE.compareAndSwapObject(this, HEAD_OFFSET, stack, null));

      RunnableExecutorPair reversedStack = null;
      while (stack != NULL_PAIR) {
        RunnableExecutorPair head = stack;

   * dataset if it were sorted. The following preconditions should hold:
   *
   * <ul>
   *   <li>{@code required}, {@code from}, and {@code to} should all be indexes into {@code array};
   *   <li>{@code required} should be in the range [{@code from}, {@code to}];
   *   <li>all the values with indexes in the range [0, {@code from}) should be less than or equal

    @Override
    @ParametricNullness
    public T get() {
      // Another variant of Double Checked Locking.
      //
      // We use two volatile reads. We could reduce this to one by
      // putting our fields into a holder class, but (at least on x86)
      // the extra memory consumption and indirection are more
      // expensive than the extra volatile reads.
      long nanos = expirationNanos;
      long now = System.nanoTime();

 * {@link ReentrantLock}, and {@code Monitor}.
 *
 * <h3>{@code synchronized}</h3>
 *
 * <p>This version is the fewest lines of code, largely because the synchronization mechanism used
 * is built into the language and runtime. But the programmer has to remember to avoid a couple of
 * common bugs: The {@code wait()} must be inside a {@code while} instead of an {@code if}, and

        : new ImmutableIntArray(array, start + startIndex, start + endIndex);
  }

  /**
   * Returns an immutable <i>view</i> of this array's values as a {@code List}; note that {@code
   * int} values are boxed into {@link Integer} instances on demand, which can be very expensive.
   * The returned list should be used once and discarded. For any usages beyond that, pass the

   * in which it will attempt to cancel itself.
   *
   * <p>An example use of this method is to convert a serializable object returned from an RPC into
   * a POJO.
   *
   * <p>This method is similar to {@link java.util.concurrent.CompletableFuture#thenApply} and
   * {@link java.util.concurrent.CompletableFuture#thenApplyAsync}. It can also serve some of the

    @Override
    public String toString() {
      return getKey() + "=" + getValue();
    }
  }

  // TODO(fry): Separate logic for consistency between emul and nonemul implementation.
  // TODO(fry): Look into Maps.KeySet and Maps.Values, which can ideally be reused here but are
  // currently only package visible.
  abstract class AbstractCacheSet<T> extends AbstractSet<T> {
    final ConcurrentMap<?, ?> map;

        : new ImmutableDoubleArray(array, start + startIndex, start + endIndex);
  }

  /**
   * Returns an immutable <i>view</i> of this array's values as a {@code List}; note that {@code
   * double} values are boxed into {@link Double} instances on demand, which can be very expensive.
   * The returned list should be used once and discarded. For any usages beyond that, pass the

@GwtCompatible(serializable = true, emulated = true)
@ElementTypesAreNonnullByDefault
final class RegularImmutableMap<K, V> extends ImmutableMap<K, V> {
  private static final byte ABSENT = -1;

  // Max size is halved due to indexing into double-sized alternatingKeysAndValues
  private static final int BYTE_MAX_SIZE = 1 << (Byte.SIZE - 1); // 2^7 = 128
  private static final int SHORT_MAX_SIZE = 1 << (Short.SIZE - 1); // 2^15 = 32_768