apollo-client/src/main/java/com/ctrip/framework/apollo/util/ConfigUtil.java/ConfigUtil/initRefreshInterval
class ConfigUtil:  private void initRefreshInterval() {
    String customizedRefreshInterval = System.getProperty("apollo.refreshInterval");
    if (!Strings.isNullOrEmpty(customizedRefreshInterval)) {
      try {
        refreshInterval = Integer.parseInt(customizedRefreshInterval);
      } catch (Throwable ex) {
        logger.error("Config for apollo.refreshInterval is invalid: {}", customizedRefreshInterval);
      }
    }
  }