* nullness checker can already "prove" are non-null. That means that the first parameter to
   * checkNotNull *should* be annotated to require it to be non-null.
   *
   * However, for a variety of reasons, Google developers have written a ton of code over the past
   * decade that assumes that they can use checkNotNull for non-precondition checks. I had hoped to

          // obj cannot be null at this point, because value can only change from null to non-null.
          // So if value changed (and it did since we lost the CAS), then it cannot be null and
          // since it isn't a SetFuture, then the future must be done and we should exit the loop
          break;
        }
      }
    }
    return rValue;
  }

  /**

      boolean sameComparator,
      Iterable<? extends Entry<? extends K, ? extends V>> entries) {
    // "adding" type params to an array of a raw type should be safe as
    // long as no one can ever cast that same array instance back to a
    // raw type.
    @SuppressWarnings("unchecked")
    Entry<K, V>[] entryArray = (Entry[]) Iterables.toArray(entries, EMPTY_ENTRY_ARRAY);

    Object key = new Object();
    assertNotNull(cache.getUnchecked(key));

    CacheTesting.simulateValueReclamation(cache, key);

    // this blocks if computation can't deal with partially-collected values
    assertNotNull(cache.getUnchecked(key));
    assertEquals(1, cache.size());
    assertEquals(2, countingLoader.getCount());

    // Can't loosen the value type:
    // Map<Number, Number> looseValued1 = transformEntries(map5, transformer);
    // Map<Number, Number> looseValued2 = transformEntries(map6, transformer);
    // Map<Integer, Number> looseValued3 = transformEntries(map8, transformer);
    // Map<Integer, Number> looseValued4 = transformEntries(map9, transformer);

    // Can't call with too loose a key:

    // Can't loosen the value type:
    // Map<Number, Number> looseValued1 = transformEntries(map5, transformer);
    // Map<Number, Number> looseValued2 = transformEntries(map6, transformer);
    // Map<Integer, Number> looseValued3 = transformEntries(map8, transformer);
    // Map<Integer, Number> looseValued4 = transformEntries(map9, transformer);

    // Can't call with too loose a key:

   * higher value than you need can waste space and time, and a significantly lower value can lead
   * to thread contention. But overestimates and underestimates within an order of magnitude do not
   * usually have much noticeable impact. A value of one permits only one thread to modify the cache
   * at a time, but since read operations and cache loading computations can proceed concurrently,

   * ordering. {@code NavigableSet} on the other hand can specify a custom ordering via a {@link
   * Comparator}, which can violate the natural ordering. Using this method (or in general using
   * {@code Range}) with unnaturally-ordered sets can lead to unexpected and undefined behavior.
   *
   * @since 20.0
   */
  @GwtIncompatible // NavigableSet

  /** Number of (unsynchronized) retries in the containsValue method. */
  static final int CONTAINS_VALUE_RETRIES = 3;

  /**
   * Number of cache access operations that can be buffered per segment before the cache's recency
   * ordering information is updated. This is used to avoid lock contention by recording a memento

   */
  public static CharMatcher whitespace() {
    return Whitespace.INSTANCE;
  }

  /**
   * Determines whether a character is a breaking whitespace (that is, a whitespace which can be
   * interpreted as a break between words for formatting purposes). See {@link #whitespace()} for a
   * discussion of that term.
   *
   * @since 19.0 (since 2.0 as constant {@code BREAKING_WHITESPACE})
   */