code: public static void compareGroup(ProviderGroup oldGroup, ProviderGroup newGroup,
                                      List<ProviderInfo> add, List<ProviderInfo> remove) {
          compareProviders(oldGroup.getProviderInfos(), newGroup.getProviderInfos(), add, remove);
      }
docs: Compare two provider group, return add list and remove list
  
  @param oldGroup old provider group
  @param newGroup new provider group
  @param add      provider list need add
  @param remove   provider list need remove