stream sorted进行降序排序 升序 降序

https://blog.csdn.net/banjw_129/article/details/83585135

    List<StaffGenderVO> genderVOList = staffList.stream()
        .collect(Collectors.groupingBy(o -> NativePlaceUtil.getCityName(o.getIdNumber()), Collectors.counting()))
        .entrySet().stream().map(e -> new StaffGenderVO(e.getKey() , e.getValue().toString()))
        .collect(Collectors.toList()).stream()
        //降序
        .sorted((h1, h2) ->  convertToInteger(h2.getValue()).compareTo( convertToInteger(h1.getValue()) ))
        //前3个
        .limit(30)
        //终止流
        .collect(Collectors.toList());

根据value值的大小进行降序排序，并进行截取。

    public static void main(String[] args) {
        List<Map<String, Object>> list = Lists.newArrayList();
        Map<String, Object> map = Maps.newHashMap();
        map.put("id", 1);
        map.put("value", 20);
        list.add(map);
        map = Maps.newHashMap();
        map.put("id", 2);
        map.put("value", 80);
        list.add(map);
        map = Maps.newHashMap();
        map.put("id", 3);
        map.put("value", 21);
        list.add(map);
        map = Maps.newHashMap();
        map.put("id", 4);
        map.put("value", 28);
        list.add(map);
        System.out.println("原始数据："+list);
        //根据value进行排序 得到升序排列
        list.sort(Comparator.comparing(h -> ConvertUtil.obj2Integer(h.get("value"))));
        //颠倒排序，变为降序排列
        Collections.reverse(list);
        //截取前3个
        System.out.println("结果"+list.subList(0, 3));
    }

使用1.8 stream处理

List<Map<String, Object>>result = list.stream().sorted((h1, h2) -> 
//降序
ConvertUtil.obj2Integer(h2.get("value")).compareTo(ConvertUtil .obj2Integer(h1.get("value"))))
				//前3个
                .limit(3)
                //终止流
                .collect(Collectors.toList());
  System.out.println("流结果"+result );

运行结果：

原始数据：[{id=1, value=20}, {id=2, value=80}, {id=3, value=21}, {id=4, value=28}]
结果[{id=2, value=80}, {id=4, value=28}, {id=3, value=21}]