if (comparator != null) { // can't use ? : because of javac bug 5080917
      return comparator;
    }
    return (Comparator<E>) Ordering.natural();
  }

  /**
   * Returns a live {@link Map} view whose keys are the contents of {@code set} and whose values are
   * computed on demand using {@code function}. To get an immutable <i>copy</i> instead, use {@link
   * #toMap(Iterable, Function)}.
   *

    map.put(four, five);
    i = map.keySet().iterator();
    i.next();
    i.remove();
    assertNotified(listener, four, five, RemovalCause.EXPLICIT);

    map.put(five, six);
    i = map.values().iterator();
    i.next();
    i.remove();
    assertNotified(listener, five, six, RemovalCause.EXPLICIT);

    assertTrue(listener.isEmpty());
  }

    assertNotified(listener, three, four, RemovalCause.EXPLICIT);

    map.put(four, five);
    i = map.keySet().iterator();
    i.next();
    i.remove();
    assertNotified(listener, four, five, RemovalCause.EXPLICIT);

    map.put(five, six);
    i = map.values().iterator();
    i.next();
    i.remove();
    assertNotified(listener, five, six, RemovalCause.EXPLICIT);

    assertTrue(listener.isEmpty());
  }

     * comments.
     */

    @Weak final LocalCache<K, V> map;

    /** The number of live elements in this segment's region. */
    volatile int count;

    /** The weight of the live elements in this segment's region. */
    @GuardedBy("this")
    long totalWeight;

    /**

     * comments.
     */

    @Weak final LocalCache<K, V> map;

    /** The number of live elements in this segment's region. */
    volatile int count;

    /** The weight of the live elements in this segment's region. */
    @GuardedBy("this")
    long totalWeight;

    /**

            return secondary;
          }
        };
    ListenableFuture<Bar> f2 = transformAsync(f1, function, directExecutor());
    f1.cancel(true);
    assertTrue(f2.isCancelled());
    /*
     * We might like to propagate interruption, too, but it's not clear that it matters. For now, we
     * test for the behavior that we have today.
     */
    assertFalse(((AbstractFuture<?>) f2).wasInterrupted());
  }

  /*

            return secondary;
          }
        };
    ListenableFuture<Bar> f2 = transformAsync(f1, function, directExecutor());
    f1.cancel(true);
    assertTrue(f2.isCancelled());
    /*
     * We might like to propagate interruption, too, but it's not clear that it matters. For now, we
     * test for the behavior that we have today.
     */
    assertFalse(((AbstractFuture<?>) f2).wasInterrupted());
  }

  /*

     * in which {@code Cursor} is {@code Closeable}. To support older versions, pass a wrapper
     * {@code Closeable} with a method reference like {@code cursor::close}.
     *
     * <p>Note that this method is still binary-compatible between flavors because the erasure of
     * its parameter type is {@code Object}, not {@code AutoCloseable} or {@code Closeable}.