public RegionEntry put() {
    serializeNewValueIfNeeded();
    runWhileLockedForCacheModification(this::doPut);
    if (isCompleted()) {
      return getRegionEntry();
    } else {
      return null;
    }
  }
@return regionEntry if put completed, otherwise null.
geode-core/src/main/java/org/apache/geode/internal/cache/map/AbstractRegionMapPut.java