@CollectionSize.Require(ZERO)
  public void testPeek_empty() {
    assertNull("emptyQueue.peek() should return null", getQueue().peek());
    expectUnchanged();
  }

  @CollectionSize.Require(ONE)
  public void testPeek_size1() {
    assertEquals("size1Queue.peek() should return first element", e0(), getQueue().peek());
    expectUnchanged();
  }

  @CollectionFeature.Require(KNOWN_ORDER)

  }

  @CanIgnoreReturnValue
  @Override
  @ParametricNullness
  public E remove() {
    return delegate().remove();
  }

  @Override
  @CheckForNull
  public E peek() {
    return delegate().peek();
  }

  @Override
  @ParametricNullness
  public E element() {
    return delegate().element();
  }

  /**

    public boolean remove(Object object) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.remove(object);
    }

    @Override
    public @Nullable E peek() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.peek();
    }

    @Override
    public E element() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.element();
    }

    @Override

    Iterator<String> nonpeek = Lists.newArrayList("a", "b", "c").iterator();
    PeekingIterator<String> peek = Iterators.peekingIterator(nonpeek);
    assertNotSame(peek, nonpeek);
    assertSame(peek, Iterators.peekingIterator(peek));
    assertSame(peek, Iterators.peekingIterator((Iterator<String>) peek));
  }

      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) {

        throw afe;
      }
    }
  }

  void checkEmpty(BlockingQueue<?> q) {
    try {
      assertTrue(q.isEmpty());
      assertEquals(0, q.size());
      assertNull(q.peek());
      assertNull(q.poll());
      assertNull(q.poll(0, MILLISECONDS));
      assertEquals("[]", q.toString());
      assertTrue(Arrays.equals(q.toArray(), new Object[0]));

  `Well, there was Mystery,' the Mock Turtle replied, counting
off the subjects on his flappers, `--Mystery, ancient and modern,
with Seaography:  then Drawling--the Drawling-master was an old
conger-eel, that used to come once a week:  HE taught us
Drawling, Stretching, and Fainting in Coils.'

  `What was THAT like?' said Alice.

  `Well, I can't show it you myself,' the Mock Turtle said:  `I'm
too stiff.  And the Gryphon never learnt it.'

    assertEquals(3, (int) mmHeap.pollLast());
    assertEquals(1, (int) mmHeap.peek());
    assertEquals(2, (int) mmHeap.peekLast());
    assertEquals(2, (int) mmHeap.pollLast());
    assertEquals(1, (int) mmHeap.peek());
    assertEquals(1, (int) mmHeap.peekLast());
    assertEquals(1, (int) mmHeap.pollLast());
    assertNull(mmHeap.peek());
    assertNull(mmHeap.peekLast());
    assertNull(mmHeap.pollLast());
  }

    segment.readCount.incrementAndGet();
    segment.count = 1;
    segment.totalWeight = 1;

    assertSame(entry, table.get(0));
    assertSame(entry, segment.accessQueue.peek());
    assertSame(entry, segment.writeQueue.peek());

    segment.clear();
    assertNull(table.get(0));
    assertTrue(segment.accessQueue.isEmpty());
    assertTrue(segment.writeQueue.isEmpty());

    segment.readCount.incrementAndGet();
    segment.count = 1;
    segment.totalWeight = 1;

    assertSame(entry, table.get(0));
    assertSame(entry, segment.accessQueue.peek());
    assertSame(entry, segment.writeQueue.peek());

    segment.clear();
    assertNull(table.get(0));
    assertTrue(segment.accessQueue.isEmpty());
    assertTrue(segment.writeQueue.isEmpty());