Java8 stream常用方法

1. 排序自定义

       从小到大排列，-1：不交换，1交换，0不处理

outpatientPresentmhVM.getMlUltrasounds().stream().sorted((o1, o2) -> {
               if (o1.getGestationalWeek() == null) {
                   return -1;
               }
               if (o2.getGestationalWeek() == null) {
                   return 1;
               }
               if (o1.getGestationalWeek() != null && o2.getGestationalWeek() != null) {
                   try {
                       String gestationalWeek1 = o1.getGestationalWeek();
                       String gestationalWeek2 = o2.getGestationalWeek();
                       if (CommonUtil.gestationalWeekToDays(gestationalWeek1) > CommonUtil.gestationalWeekToDays(gestationalWeek2)) {
                           return 1;
                       } else {
                           return -1;
                       }
                   } catch (Exception e) {
                       e.printStackTrace();
                   }
               }
               return 0;
           }).collect(Collectors.toList());

2.分组

Map>> groupData = listMapData.stream().collect(Collectors.groupingBy(o -> o.get("age")));
Map>> grouptwoData = listMapData.stream().collect(Collectors.groupingBy(o -> o.get("age")+"_"+o.get("name")));
System.out.println("根据年龄分组后的数据："+groupData);
System.out.println("根据年龄+姓名分组后的数据："+grouptwoData);