* creation and removal (including automatic removal of zeroes). If the modification of an
   * AtomicInteger results in zero, we compareAndSet the value to zero; if that succeeds, we remove
   * the entry from the Map. If another operation sees a zero in the map, it knows that the entry is
   * about to be removed, so this operation may remove it (often by replacing it with a new
   * AtomicInteger).
   */

   * creation and removal (including automatic removal of zeroes). If the modification of an
   * AtomicInteger results in zero, we compareAndSet the value to zero; if that succeeds, we remove
   * the entry from the Map. If another operation sees a zero in the map, it knows that the entry is
   * about to be removed, so this operation may remove it (often by replacing it with a new
   * AtomicInteger).
   */

      entrySet.remove(entryOf(2, 2));
      assertFalse(entrySet.remove(null));
      assertFalse(entrySet.remove(entryOf(1, 1)));
      assertFalse(entrySet.remove(entryOf(6, 6)));
      assertFalse(entrySet.removeAll(asList(null, entryOf(1, 1), entryOf(15, 15))));
      assertFalse(entrySet.retainAll(asList(null, entryOf(1, 1), entryOf(15, 15))));
      checkEmpty(entrySet);
      checkEmpty(cache);
    }
  }

      }
    }

    /**
     * Removes <b>all</b> occurrences of the specified element from this multiset. This method
     * complements {@link Multiset#remove(Object)}, which removes only one occurrence at a time.
     *
     * @param element the element whose occurrences should all be removed
     * @return the number of occurrences successfully removed, possibly zero
     */

      }
    }

    /**
     * Removes <b>all</b> occurrences of the specified element from this multiset. This method
     * complements {@link Multiset#remove(Object)}, which removes only one occurrence at a time.
     *
     * @param element the element whose occurrences should all be removed
     * @return the number of occurrences successfully removed, possibly zero
     */

    AtomicLong atomic = map.get(key);
    if (atomic == null) {
      return false;
    }

    long oldValue = atomic.get();
    if (oldValue != value) {
      return false;
    }

    if (oldValue == 0L || atomic.compareAndSet(oldValue, 0L)) {
      // only remove after setting to zero, to avoid concurrent updates
      map.remove(key, atomic);

      entrySet.remove(entryOf(2, 2));
      assertFalse(entrySet.remove(null));
      assertFalse(entrySet.remove(entryOf(1, 1)));
      assertFalse(entrySet.remove(entryOf(6, 6)));
      assertFalse(entrySet.removeAll(asList(null, entryOf(1, 1), entryOf(15, 15))));
      assertFalse(entrySet.retainAll(asList(null, entryOf(1, 1), entryOf(15, 15))));
      checkEmpty(entrySet);
      checkEmpty(cache);
    }
  }

  @Override
  @CheckForNull
  public V remove(@CheckForNull Object rowKey, @CheckForNull Object columnKey) {
    if ((rowKey == null) || (columnKey == null)) {
      return null;
    }
    Map<C, V> map = safeGet(backingMap, rowKey);
    if (map == null) {
      return null;
    }
    V value = map.remove(columnKey);
    if (map.isEmpty()) {
      backingMap.remove(rowKey);
    }
    return value;
  }

   *
   * <p>This method refines {@link Collection#remove} to further specify that it <b>may not</b>
   * throw an exception in response to {@code element} being null or of the wrong type.
   *
   * <p>To both remove the element and obtain the previous count of that element, use {@link
   * #remove(Object, int) remove}{@code (element, 1)} instead.
   *
   * @param element the element to remove one occurrence of

    assertEquals((Integer) 2, it.next());
    it.remove();
    // After this remove, 400 has moved up and 20 down past cursor
    assertTrue("Heap is not intact after remove", mmHeap.isIntact());
    assertEquals((Integer) 10, it.next());
    assertEquals((Integer) 3, it.next());
    it.remove();
    // After this remove, 400 moved down again and 500 up past the cursor