code: public static Single<Long> length(CacheConfigBean cacheConfigBean, String cacheKey) {
          return SingleRxXian.call(CacheService.CACHE_SERVICE, "cacheListLength", new JSONObject() {{
              put("cacheConfig", cacheConfigBean);
              put("key", cacheKey);
          }}).map(unitResponse -> {
              long length = Objects.requireNonNull(unitResponse.dataToLong());
              return length > 0 ? length : 0;
          });
      }
docs: query the length of the cached list
  
  @param cacheConfigBean the cache data source
  @param cacheKey        the key for the cached list
  @return the cached list's length