jdk1.8 集合操作

/**
 * JDK1.8的学习
 */

public class Test {

   public static void main(String[] args)
   {
       ModelService modelService = (ModelService) SpringUtil.getBean("modelServiceImpl");

       //       1.对象创建: 使用lombok注解
       //       @Data
       //       @NoArgsConstructor
       //       @AllArgsConstructor

       //2. list或者map创建
       Map<String, Integer> map = Maps.newHashMap();
       List<Map.Entry<String, Integer>> dataList = Lists.newArrayList(map.entrySet());

       //3.1 list转map
       List<RankVo> list1 =  Lists.newArrayList();
       Map<String, RankVo> appleMap = list1.stream().collect(Collectors.toMap(RankVo::getModelLabel, e -> e,(k1,k2)->k1));
       Map<String, String> dataIdLogicIdMap = list1.stream().collect(Collectors.toMap(e -> e.getModelLabel(), e -> e.getName(), (k1, k2) -> k1));

       //3.2 list统计后转map
       List<DevicesInPlaceVo> devicesInPlaceVos = Lists.newArrayList();
       Map<String, Integer> peceventcountTypeMap = new HashMap<>(16);
       devicesInPlaceVos.stream().forEach(e -> peceventcountTypeMap.merge(e.getModelLabel(),e.getId().intValue(), Integer::sum));

       //3.3 list分组转map
       Map<String, List<RankVo>> rankMap = list1.stream().collect(Collectors.groupingBy(RankVo::getModelLabel));


       //4.字段筛选,去重
       List list3 = Lists.newArrayList();
       //List<Long> deviceIds = list3.stream().map(e -> e.getMeasuredby()).distinct().collect(Collectors.toList());

       //5.集合枚举
       List<String> EVENT_LEVEL_IN_STRING = Stream.of("事故", "告警", "一般", "预警", "其他").collect(Collectors.toList());

       //6.统计
       List<Map> queryList =  Lists.newArrayList();
       int count = queryList.stream().mapToInt(e -> Integer.valueOf(e.get("count").toString())).sum();

       //7.过滤,取均值
       //最大值
       //Double maxuabValue = allList.stream().filter(e -> e.get("uab") != null).mapToDouble(e -> (Double) e.get("uab")).max().getAsDouble();
       // 最小值
       //Double minuabValue = allList.stream().filter(e -> e.get("uab") != null).mapToDouble(e -> (Double) e.get("uab")).min().getAsDouble();
       // 平均值
       //Double averageuabValue = allList.stream().filter(e -> e.get("uab") != null).mapToDouble(e -> (Double) e.get("uab")).average().getAsDouble();

       //8.查找任何一个
       DevicesInPlaceVo dcbaseDeviceInfo = devicesInPlaceVos.stream().findAny().orElse(null);

       //9.统计字段总数
       List<PecEventCountVo> pecEventCountVos = Lists.newArrayList();
       int totalCount = pecEventCountVos.stream().collect(Collectors.summingInt(vo -> (vo.getCount())));
   }
}

 

本文地址：https://blog.csdn.net/t194978/article/details/109853774