1、对象list中取某一个元素形成新的数组

bridgeInfos.stream().map(NavigableBridgePO::getId).collect(Collectors.toList());

2、对象list中按某个元素分组形成新的map

Map<String,List<ProjectFilePO>> projectFileMap = projectFilePOS.stream().collect(Collectors.groupingBy(ProjectFilePO::getFileBusinessId));

3、对象list中按某个元素排序形成新的list

List<FileInfoPO> collect = fileInfoPOList.stream().sorted(Comparator.comparing(FileInfoPO::getName).reversed()).collect(Collectors.toList());

4、对象list筛选某些对象出来形成新的list

        list = list.stream().filter(p -> CommonConstant.DEPT_SORT_LONG.contains((p.getDeptId()))).collect(Collectors.toList());