需求分解做法记录
功能：先按名称分组然后，组内从低到高排序，然后每组排序

做法一：

List<CruiseDetailOutputDto> result =  new ArrayList<CruiseDetailOutputDto>();List<CruiseDetailOutputDto> journeyCruiseList =  new ArrayList<CruiseDetailOutputDto>();journeyCruiseList.add(new CruiseDetailOutputDto("*虚拟阳台双人内舱房-4U", new BigDecimal(7798)));journeyCruiseList.add(new CruiseDetailOutputDto("*虚拟阳台双人内舱房-4U", new BigDecimal(7148)));journeyCruiseList.add(new CruiseDetailOutputDto("*船中虚拟阳台双人内舱房-2U", new BigDecimal(7810)));journeyCruiseList.add(new CruiseDetailOutputDto("*船中虚拟阳台双人内舱房-2U", new BigDecimal(7606)));journeyCruiseList.add(new CruiseDetailOutputDto("*船中虚拟阳台家庭内舱四人间-1U", new BigDecimal(9814)));journeyCruiseList.add(new CruiseDetailOutputDto("*船中虚拟阳台家庭内舱四人间-1U", new BigDecimal(11143)));journeyCruiseList.add(new CruiseDetailOutputDto("*豪华阳台三人间-1C", new BigDecimal(14522)));journeyCruiseList.add(new CruiseDetailOutputDto("*豪华阳台三人间-1C", new BigDecimal(17247)));Map<String, List<CruiseDetailOutputDto>> resourceMap = new LinkedHashMap<String, List<CruiseDetailOutputDto>>();for (CruiseDetailOutputDto cruiseDetailOutputDto : journeyCruiseList) {if (!resourceMap.containsKey(cruiseDetailOutputDto.getRoomName())) {resourceMap.put(cruiseDetailOutputDto.getRoomName(), new ArrayList<CruiseDetailOutputDto>());}resourceMap.get(cruiseDetailOutputDto.getRoomName()).add(cruiseDetailOutputDto);}List<List<CruiseDetailOutputDto>> groupsSort = new ArrayList<List<CruiseDetailOutputDto>>(resourceMap.values());for (List<CruiseDetailOutputDto> cruiseDetailOutputDtos : groupsSort) {Collections.sort(cruiseDetailOutputDtos, new Comparator<CruiseDetailOutputDto>() {public int compare(CruiseDetailOutputDto a, CruiseDetailOutputDto b) {return a.getMainResPrice().compareTo(b.getMainResPrice());}});}// 2.按分组中的最低价格重新排序分组List<List<CruiseDetailOutputDto>> groups = new ArrayList<List<CruiseDetailOutputDto>>(resourceMap.values());Collections.sort(groups, new Comparator<List<CruiseDetailOutputDto>>() {public int compare(List<CruiseDetailOutputDto> a, List<CruiseDetailOutputDto> b) {return a.get(0).getMainResPrice().compareTo(b.get(0).getMainResPrice());}});for (List<CruiseDetailOutputDto> group : groups) {for (CruiseDetailOutputDto cruiseDetailOutputDto : group) {result.add(cruiseDetailOutputDto);System.out.println(cruiseDetailOutputDto);}}

做法二

public static void main(String[] args) {List<Item> items = Arrays.asList(new Item("A", 3),new Item("B", 2),new Item("A", 1),new Item("B", 4),new Item("C", 1));// 按名称分组，然后组内从低到高排序Map<String, List<Item>> groupedAndSorted = items.stream().collect(Collectors.groupingBy(Item::getName,Collectors.mapping(item -> item, Collectors.toList()))).entrySet().stream().collect(Collectors.toMap(Map.Entry::getKey,entry -> entry.getValue().stream().sorted((a, b) -> a.getValue() - b.getValue()).collect(Collectors.toList())));// 每组排序List<Item> result = groupedAndSorted.entrySet().stream().sorted(Map.Entry.comparingByKey()).flatMap(entry -> entry.getValue().stream()).collect(Collectors.toList());System.out.println(result);}