public void clear() {
      ReferenceEntry<K, V> e = head.getNextInWriteQueue();
      while (e != head) {
        ReferenceEntry<K, V> next = e.getNextInWriteQueue();
        nullifyWriteOrder(e);
        e = next;
      }

      head.setNextInWriteQueue(head);
      head.setPreviousInWriteQueue(head);
    }

    @Override
    public Iterator<ReferenceEntry<K, V>> iterator() {

    ticker.advance(1);
    segment.recordRead(entry, ticker.read());
    segment.expireEntries(ticker.read());
    assertTrue(map.containsKey(key));
    assertSame(entry, segment.accessQueue.peek());
    assertEquals(1, segment.accessQueue.size());

    ticker.advance(1);
    segment.recordRead(entry, ticker.read());
    segment.expireEntries(ticker.read());
    assertTrue(map.containsKey(key));

    ticker.advance(1);
    segment.recordRead(entry, ticker.read());
    segment.expireEntries(ticker.read());
    assertTrue(map.containsKey(key));
    assertSame(entry, segment.accessQueue.peek());
    assertEquals(1, segment.accessQueue.size());

    ticker.advance(1);
    segment.recordRead(entry, ticker.read());
    segment.expireEntries(ticker.read());
    assertTrue(map.containsKey(key));

How she longed to get out of that dark hall, and wander about
among those beds of bright flowers and those cool fountains, but
she could not even get her head though the doorway; `and even if
my head would go through,' thought poor Alice, `it would be of
very little use without my shoulders.  Oh, how I wish
I could shut up like a telescope!  I think I could, if I only

    public void clear() {
      ReferenceEntry<K, V> e = head.getNextInWriteQueue();
      while (e != head) {
        ReferenceEntry<K, V> next = e.getNextInWriteQueue();
        nullifyWriteOrder(e);
        e = next;
      }

      head.setNextInWriteQueue(head);
      head.setPreviousInWriteQueue(head);
    }

    @Override
    public Iterator<ReferenceEntry<K, V>> iterator() {

How she longed to get out of that dark hall, and wander about
among those beds of bright flowers and those cool fountains, but
she could not even get her head though the doorway; `and even if
my head would go through,' thought poor Alice, `it would be of
very little use without my shoulders.  Oh, how I wish
I could shut up like a telescope!  I think I could, if I only

    return Synchronized.biMap(bimap, null);
  }

  /**
   * Returns an unmodifiable view of the specified bimap. This method allows modules to provide
   * users with "read-only" access to internal bimaps. Query operations on the returned bimap "read
   * through" to the specified bimap, and attempts to modify the returned map, whether direct or via
   * its collection views, result in an {@code UnsupportedOperationException}.
   *