static class MyServerExampleWithFrq implements Closeable {
    private static final FinalizableReferenceQueue frq = new FinalizableReferenceQueue();

    private static final Set<Reference<?>> references = Sets.newConcurrentHashSet();

    private final ServerSocket serverSocket;

    private MyServerExampleWithFrq() throws IOException {
      this.serverSocket = new ServerSocket(0);
    }

   * @throws NullPointerException if {@code elements} or any of its contents is null
   * @since 15.0
   */
  public static <E> Set<E> newConcurrentHashSet(Iterable<? extends E> elements) {
    Set<E> set = newConcurrentHashSet();
    Iterables.addAll(set, elements);
    return set;
  }

  // LinkedHashSet

  /**
   * Creates a <i>mutable</i>, empty {@code LinkedHashSet} instance.

  }

  private static final class RecordingListener extends ServiceManager.Listener {
    volatile boolean healthyCalled;
    volatile boolean stoppedCalled;
    final Set<Service> failedServices = Sets.newConcurrentHashSet();

    @Override
    public void healthy() {
      healthyCalled = true;
    }

    @Override
    public void stopped() {
      stoppedCalled = true;
    }

    @Override