"Should be able to peek() middle element multiple times", "B", peekingIterator.peek());
    assertEquals(
        "next() should still return middle element after peeking", "B", peekingIterator.next());

    assertEquals("Should be able to peek() at last element", "C", peekingIterator.peek());
    assertEquals(
        "Should be able to peek() last element multiple times", "C", peekingIterator.peek());
    assertEquals(

    assertTrue(queue.add("hi"));
    assertEquals("hi", queue.element());
    assertEquals("hi", queue.peek());
    assertEquals(1, queue.size());
    assertEquals(0, queue.remainingCapacity());

    assertTrue(queue.add("there"));
    assertEquals("there", queue.element());
    assertEquals("there", queue.peek());
    assertEquals(1, queue.size());
    assertEquals(0, queue.remainingCapacity());

   * contract of {@link PeekingIterator#peek()}.
   *
   * <p>Implementations of {@code AbstractIterator} that wish to expose this functionality should
   * implement {@code PeekingIterator}.
   */
  @ParametricNullness
  public final T peek() {
    if (!hasNext()) {
      throw new NoSuchElementException();
    }

    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

    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());
  }

   * @throws IOException if an I/O error occurs
   */
  @CanIgnoreReturnValue // to skip a line
  @CheckForNull
  public String readLine() throws IOException {
    while (lines.peek() == null) {
      Java8Compatibility.clear(cbuf);
      // The default implementation of Reader#read(CharBuffer) allocates a
      // temporary char[], so we call Reader#read(char[], int, int) instead.

   *     Iterators.peekingIterator(Iterators.forArray("a", "b"));
   * String a1 = peekingIterator.peek(); // returns "a"
   * String a2 = peekingIterator.peek(); // also returns "a"
   * String a3 = peekingIterator.next(); // also returns "a"
   * }</pre>
   *
   * <p>Any structural changes to the underlying iteration (aside from those performed by the

    } finally {
      monitor.leave();
    }
  }

  @CanIgnoreReturnValue // pushed down from class to method
  @Override
  public @Nullable E peek() {
    final Monitor monitor = this.monitor;
    monitor.enter();
    try {
      return q.peek();
    } finally {
      monitor.leave();
    }
  }

  /**

    Object one = new Object();
    assertSame(one, cache.getUnchecked(one));
    assertTrue(segment.recencyQueue.isEmpty());
    assertSame(one, map.get(one));
    assertSame(one, segment.recencyQueue.peek().getKey());
    assertSame(one, cache.getUnchecked(one));
    assertFalse(segment.recencyQueue.isEmpty());
  }

  public void testRecursiveComputation() throws InterruptedException {

  @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)