public class PageUtil {

    public static <T> List<T> memoryPaging(List<T> dataList, long pageNum, long pageSize) {
        if (CollectionUtils.isEmpty(dataList)){
            return Collections.emptyList();
        }
        if (pageNum <= 0 || pageSize <= 0) {
            return Collections.emptyList();
        }
        return dataList.stream().skip((pageNum-1)*pageSize).limit(pageSize).collect(Collectors.toList());
    }
}