*     monitor.enterWhen(valueAbsent);
 *     try {
 *       value = newValue;
 *     } finally {
 *       monitor.leave();
 *     }
 *   }
 * }
 * }</pre>
 *
 * @author Justin T. Sampson
 * @author Martin Buchholz
 * @since 10.0
 */
@J2ktIncompatible
@GwtIncompatible
@SuppressWarnings("GuardedBy") // TODO(b/35466881): Fix or suppress.
@ElementTypesAreNonnullByDefault