} catch (ExecutionException expected) {
                  }
                  try {
                    peeker.getDone(nonInput);
                    fail("Peeker should not be able to peek into non-input ClosingFuture.");
                  } catch (IllegalArgumentException expected) {
                  }
                  capturedPeeker.set(peeker);
                  return closeable2;
                },

      drainRecencyQueue();

      ReferenceEntry<K, V> e;
      while ((e = writeQueue.peek()) != null && map.isExpired(e, now)) {
        if (!removeEntry(e, e.getHash(), RemovalCause.EXPIRED)) {
          throw new AssertionError();
        }
      }
      while ((e = accessQueue.peek()) != null && map.isExpired(e, now)) {
        if (!removeEntry(e, e.getHash(), RemovalCause.EXPIRED)) {

      if (source.isEmpty()) {
        throw PermittedMetaException.NSEE;
      }

      destination.push(source.pop());
      stackWithLastReturnedElementAtTop = destination;
      return destination.peek();
    }

    private void throwIfInvalid(IteratorFeature methodFeature) {
      if (!features.contains(methodFeature)) {
        if (stackWithLastReturnedElementAtTop == null) {

    monitor.enterWhen(notEmpty);
    try {
      return extract();
    } finally {
      monitor.leave();
    }
  }

  @CanIgnoreReturnValue
  @Override
  public @Nullable E peek() {
    Monitor monitor = this.monitor;
    if (monitor.enterIf(notEmpty)) {
      try {
        return items[takeIndex];
      } finally {
        monitor.leave();
      }
    } else {

      while (peekingItr.hasNext()) {
        Range<C> range = peekingItr.next();
        while (peekingItr.hasNext()) {
          Range<C> nextRange = peekingItr.peek();
          if (range.isConnected(nextRange)) {
            checkArgument(
                range.intersection(nextRange).isEmpty(),
                "Overlapping ranges not permitted but found %s overlapping %s",

      while (peekingItr.hasNext()) {
        Range<C> range = peekingItr.next();
        while (peekingItr.hasNext()) {
          Range<C> nextRange = peekingItr.peek();
          if (range.isConnected(nextRange)) {
            checkArgument(
                range.intersection(nextRange).isEmpty(),
                "Overlapping ranges not permitted but found %s overlapping %s",

    Deque<NodeAndRemainingSuccessors<N>> stack = new ArrayDeque<>();
    stack.addLast(new NodeAndRemainingSuccessors<>(startNode));

    while (!stack.isEmpty()) {
      // To peek at the top two items, we need to temporarily remove one.
      NodeAndRemainingSuccessors<N> top = stack.removeLast();
      NodeAndRemainingSuccessors<N> prev = stack.peekLast();
      stack.addLast(top);

		}
	}
}

func Test_metacacheReader_peek(t *testing.T) {
	r := loadMetacacheSample(t)
	defer r.Close()
	for i, want := range loadMetacacheSampleNames {
		got, err := r.peek()
		if err == io.EOF {
			break
		}
		if err != nil {
			t.Fatal(err)
		}
		if got.name != want {
			t.Errorf("entry %d, want %q, got %q", i, want, got.name)
		}
		gotObj, err := r.next()

    public boolean offer(E e) {
      synchronized (mutex) {
        return delegate().offer(e);
      }
    }

    @Override
    public @Nullable E peek() {
      synchronized (mutex) {
        return delegate().peek();
      }
    }

    @Override
    public @Nullable E poll() {
      synchronized (mutex) {
        return delegate().poll();
      }
    }

    public boolean offer(E e) {
      synchronized (mutex) {
        return delegate().offer(e);
      }
    }

    @Override
    public @Nullable E peek() {
      synchronized (mutex) {
        return delegate().peek();
      }
    }

    @Override
    public @Nullable E poll() {
      synchronized (mutex) {
        return delegate().poll();
      }
    }