Java過濾集合

public RestResult<List<UserBelongsItemsVO>> getUserBelongsItems(EmptyParam param) {
    List<UserBelongsItemsVO> results = new ArrayList<>();
    List<CommunityUser> communityUserList= communityUserBaseService.getValidInfoByMemberId(param);
    List<CommunityUser> collect = communityUserList.parallelStream().filter(distinctByKey(CommunityUser::getCommunityCode)).collect(Collectors.toList());
    return RestResult.wrapSuccessResponse(results);
}

public static <T> Predicate<T> distinctByKey(Function<? super T, ?> keyExtractor) {
    Set<Object> seen = ConcurrentHashMap.newKeySet();
    return t -> seen.add(keyExtractor.apply(t));
}