* called multiple times.
   *
   * <p>If {@link #stopAsync} is called on a {@link State#STARTING} service, this method is not
   * invoked immediately. Instead, it will be deferred until after the service is {@link
   * State#RUNNING}. Services that need to cancel startup work can override {@link #doCancelStart}.
   */
  @ForOverride
  protected abstract void doStop();

  /**

          put(closeable, executor);
          return;
        }
      }
      closeQuietly(closeable, executor);
    }

    /**
     * Returns a latch that reaches zero when this objects' deferred closeables have been closed.
     */
    CountDownLatch whenClosedCountDown() {
      if (closed) {
        return new CountDownLatch(0);
      }
      synchronized (this) {
        if (closed) {

@ElementTypesAreNonnullByDefault
final class Platform {
  /** Returns the platform preferred implementation of a map based on a hash table. */
  static <K extends @Nullable Object, V extends @Nullable Object>
      Map<K, V> newHashMapWithExpectedSize(int expectedSize) {
    return CompactHashMap.createWithExpectedSize(expectedSize);
  }

  /**
   * Returns the platform preferred implementation of an insertion ordered map based on a hash
   * table.
   */

  // execution significantly)

  /**
   * This classloader disallows {@link sun.misc.Unsafe}, which will prevent us from selecting our
   * preferred strategy {@code UnsafeAtomicHelper}.
   */
  private static final ClassLoader NO_UNSAFE =
      getClassLoader(ImmutableSet.of(sun.misc.Unsafe.class.getName()));

  /**

   * write operations. Expired entries are cleaned up as part of the routine maintenance described
   * in the class javadoc.
   *
   * <p>If you can represent the duration as a {@link java.time.Duration} (which should be preferred
   * when feasible), use {@link #expireAfterWrite(Duration)} instead.
   *
   * @param duration the length of time after an entry is created that it should be automatically
   *     removed

   * the path {@code a/../b}, which {@code simplifyPath} will change to {@code b}. If {@code a} is a
   * symlink to {@code x}, {@code a/../b} may refer to a sibling of {@code x}, rather than the
   * sibling of {@code a} referred to by {@code b}.
   *
   * @since 11.0
   */
  public static String simplifyPath(String pathname) {
    checkNotNull(pathname);
    if (pathname.length() == 0) {
      return ".";
    }

  /**
   * Start of Heading: A communication control character used at the beginning of a sequence of
   * characters which constitute a machine-sensible address or routing information. Such a sequence
   * is referred to as the "heading." An STX character has the effect of terminating a heading.
   *
   * @since 8.0
   */
  public static final byte SOH = 1;

  /**

  // http://docs.oracle.com/javase/6/docs/technotes/guides/security/crypto/CryptoSpec.html
  //  - Some providers may choose to also include alias names.
  //  - For example, the "SHA-1" algorithm might be referred to as "SHA1".
  //  - The algorithm name is not case-sensitive.
  private static final ImmutableMap<String, HashFunction> ALGORITHMS =
      new ImmutableMap.Builder<String, HashFunction>()
          .put("MD5", Hashing.md5())

  static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
    return CollectCollectors.toImmutableSet();
  }

  /**
   * Returns the empty immutable set. Preferred over {@link Collections#emptySet} for code
   * consistency, and because the return type conveys the immutability guarantee.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */

  /**
   * The HTTP <a href="https://www.w3.org/TR/referrer-policy/">{@code Referrer-Policy}</a> header
   * field name.
   *
   * @since 23.4
   */
  public static final String REFERRER_POLICY = "Referrer-Policy";

  /**
   * Values for the <a href="https://www.w3.org/TR/referrer-policy/">{@code Referrer-Policy}</a>
   * header.
   *
   * @since 23.4
   */