java8 stream常见用法

TreeMap> tempMap = infoArticles.parallelStream()
            .collect(Collectors.groupingBy(
                    vo->DateUtil.format(vo.getCreateTime(), "yyyy-MM-dd"),
                    () -> new TreeMap<>((o1, o2) -> Math.toIntExact(Long.parseLong(o2.replaceAll("-","")) - Long.parseLong(o1.replaceAll("-","")))),
                    Collectors.toList())
            );

        //将集合中所有数据按照父Id进行分组，放入Map中，Map>
        Map> groupByParentIdMap = data.stream().collect(Collectors.groupingBy(item -> item.root() ? "" : Objects.toString(item.getPid())));
        
        //将集合中所有数据以数据Id为key，放入Map中，Map
        Map dataMap = data.stream().collect(Collectors.toMap(item -> item.getId().toString(), t -> t));