Builds a thread-safe map, without on-demand computation of values. This method does not alter the state of this {@code MapMaker} instance, so it can be invoked again to create multipleindependent maps.
The bulk operations {@code putAll}, {@code equals}, and {@code clear} are not guaranteed tobe performed atomically on the returned map. Additionally, {@code size} and {@code containsValue} are implemented as bulk read operations, and thus may fail to observe concurrentwrites.
@return a serializable concurrent map having the requested features