public static <T> void updateMapHelper(Map<T, Long> map, T key, Long value) {
    Long newValue = map.containsKey(key) ? map.get(key) + value : value;
    map.put(key, newValue);
  }
Helper function to update map data structure.
@param map {@link Map} to be updated
@param key of the map
@param value the value to be added at the corresponding entry
ambry-store/src/main/java/com/github/ambry/store/StatsUtils.java