Linq

1、filter：删选

list.stream().filter(x -> Objects.equals(x.getId(), saleUserId)).collect(Collectors.toList());

2、map：映射某个字段

List<Integer> businessIds = businesslist.stream().map(Business::getId).collect(Collectors.toList());

3、group：分组

 /**
         * 根据作品编码分组
         */
        Map<String, List<ExportExcelTemplateVo>> groupBy = list.stream().collect(Collectors.groupingBy(ExportExcelTemplateVo::getWorksItemNo));