java 8 怎么把三个list分组然后合并到一个list里面？

Question

list1

{"hjje":"520.00","dan_no":"YSQ2022102"},{"hjje":"351.02","dan_no":"YSQ202206"}

list2

{"shum":"JAVA","dan_no":"YSQ202206"},{"shum":"C++","dan_no":"YSQ2022102"},{"shum":"PHP","dan_no":"YSQ202206"}

list3

{"nj":"三年级二班","dan_no":"YSQ202206"},{"nj":"二年级一班","dan_no":"YSQ2022102"},{"nj":"三年级四班","dan_no":"YSQ202206"},

java8 怎么把上面3个List根据dan_no分组，然后合并到一个List里面？
最终结果：

{"dan_no":"YSQ2022102","shum":"C++","nj":"二年级一班","hjje":"520.00"},{"dan_no":"YSQ202206","shum":"JAVA,PHP","nj":"三年级四班,三年级二班","hjje":"351.02"}

初学，请教。

Answer 1

public static void main(String[] args) {
        List<Map<String,String>> list1 = new ArrayList<>();
        Map<String,String> map11 = new HashMap();
        map11.put("hjje", "520.00");
        map11.put("dan_no", "YSQ2022102");

        Map<String,String> map12 = new HashMap();
        map12.put("hjje", "351.02");
        map12.put("dan_no", "YSQ202206");
        list1.add(map11);
        list1.add(map12);

        List<Map<String,String>> list2 = new ArrayList<>();
        Map<String,String> map21 = new HashMap();
        map21.put("shum", "JAVA");
        map21.put("dan_no", "YSQ202206");

        Map<String,String> map22 = new HashMap();
        map22.put("shum", "C++");
        map22.put("dan_no", "YSQ2022102");

        Map<String,String> map23 = new HashMap();
        map23.put("shum", "PHP");
        map23.put("dan_no", "YSQ202206");
        list2.add(map21);
        list2.add(map22);
        list2.add(map23);

        List<Map<String,String>> list3 = new ArrayList<>();
        Map<String,String> map31 = new HashMap();
        map31.put("nj", "三年级二班");
        map31.put("dan_no", "YSQ202206");

        Map<String,String> map32 = new HashMap();
        map32.put("nj", "二年级一班");
        map32.put("dan_no", "YSQ2022102");

        Map<String,String> map33 = new HashMap();
        map33.put("nj", "三年级四班");
        map33.put("dan_no", "YSQ202206");

        list3.add(map31);
        list3.add(map32);
        list3.add(map33);
        List<Map<String, String>> collect2 = list1.stream().map(m1 -> {
            List<String> collect = list2.stream().filter(f -> m1.get("dan_no").equals(f.get("dan_no"))).map(fe -> {
                String shum = fe.get("shum").toString();
                return shum;
            }).collect(Collectors.toList());
            String join = String.join(",", collect);
            m1.put("shum", join);

            List<String> collect1 = list3.stream().filter(f -> m1.get("dan_no").equals(f.get("dan_no"))).map(fe -> {
                String shum = fe.get("nj").toString();
                return shum;
            }).collect(Collectors.toList());
            String nj = String.join(",", collect1);
            m1.put("nj", nj);
            return m1;
        }).collect(Collectors.toList());
        System.out.println(collect2);
    }