對List集合裡儲存的map其中一個key的值，進行排序

1.對List集合裡儲存的map其中一個key的值，進行排序

   例：

 List<Map<String, Object>> list= new ArrayList();

注：list裡面存在 name屬性

//排序 倒序 對key為name 的值進行排序

if (!getList.isEmpty()) {

    Collections.sort(list, new Comparator<Map<String, Object>>() {

        @Override

        public int compare(Map<String, Object> o1, Map<String, Object> o2) {

            Integer o1Value = Integer.valueOf(o1.get("count").toString());

            Integer o2Value = Integer.valueOf(o2.get("count").toString());

            return o2Value.compareTo(o1Value);

        }

    });

}

//正序就把值反過來 ： return o1Value.compareTo(o2Value);

2.還可以以流的形式進行排序，多字段進行排序

private static int comparator(Object o, Object o1) {
    Map map1 = Convert.convert(Map.class, o);
    Map map2 = Convert.convert(Map.class, o1);
    if (map1 == null && map2 == null)

        return 0;
    if (map1 == null || map2 == null) {

        throw new NullPointerException();
    }

    String name1 = (String) map1.get("name");

    String name2 = (String) map2.get("name");

    int c = name1.compareTo(name2);

    if (c != 0)

        return c;

    int age1 = (int) map1.get("age");

    int age2 = (int) map2.get("age");

    return age2 - age1;
}      

public static void main(String[] args) {
    Map map = new HashMap();

    map.put("name", "張三");

    map.put("age", 22);

    Map map2 = new HashMap();

    map2.put("name", "李四");

    map2.put("age", 25);

    Map map3 = new HashMap();

    map3.put("name", "王五");

    map3.put("age", 26);

    Map map4 = new HashMap();

    map4.put("name", "錢七");

    map4.put("age", 28);

    List list = new ArrayList();

    list.add(map);

    list.add(map2);

    list.add(map3);

    list.add(map4);

    Stream stream = list.stream();

    List<Map>list2=(List<Map>)stream.sorted(Demo::comparator).collect(Collectors.toList());

    for (Map m : list2) {

        System.out.println(m.get("name") + " " + m.get("age"));

    }

}