secondSignal.await();

    // start waiting thread
    new Thread() {
      @Override
      public void run() {
        thirdSignal.countDown();
        result.set(1, cache.getUnchecked(key));
        doneSignal.countDown();
      }
    }.start();

    // give the second get a chance to run; it is okay for this to be racy

    secondSignal.await();

    // start waiting thread
    new Thread() {
      @Override
      public void run() {
        thirdSignal.countDown();
        result.set(1, cache.getUnchecked(key));
        doneSignal.countDown();
      }
    }.start();

    // give the second get a chance to run; it is okay for this to be racy

        if (setmid) {
            makeKey(req);
        } else {
            req.setMid(0);
            this.mid.set(1);
        }
        final int n = req.encode(this.sbuf, 4);
        Encdec.enc_uint32be(n & 0xFFFF, this.sbuf, 0); /* 4 byte ssn msg header */

        if (log.isTraceEnabled()) {

   *
   * <p>Results are undefined if {@code set1} and {@code set2} are sets based on different
   * equivalence relations, for example if {@code set1} is a {@link HashSet} and {@code set2} is a
   * {@link TreeSet} or the {@link Map#keySet} of an {@code IdentityHashMap}.
   */
  public static <E extends @Nullable Object> SetView<E> difference(Set<E> set1, Set<?> set2) {
    checkNotNull(set1, "set1");

   */
  public static <E extends @Nullable Object> SetView<E> union(
      Set<? extends E> set1, Set<? extends E> set2) {
    checkNotNull(set1, "set1");
    checkNotNull(set2, "set2");

    return new SetView<E>() {
      @Override
      public int size() {
        int size = set1.size();
        for (E e : set2) {
          if (!set1.contains(e)) {
            size++;
          }
        }
        return size;