java-stream-根据某个字段去重

public static void main(String[] args) {
List<User> userList = new ArrayList<>();
userList.add(new User("1","李大锤","23","南京"));
userList.add(new User("2","张无忌","18","西安"));
userList.add(new User("3","刘德华","26","苏州"));
userList.add(new User("4","郭靖","33","上海"));

userList.add(new User("1","李大锤","23","南京"));
userList.add(new User("3","带头大哥","36","杭州"));
System.out.println("原数据"+userList);

userList = userList.stream()
.collect(Collectors.collectingAndThen(Collectors
.toCollection(()->new TreeSet<>(Comparator.comparing(User::getId))), ArrayList::new));

System.out.println("现数据"+userList);


}

 

原数据：[User(id=1, username=李大锤, password=23, address=南京), User(id=2, username=张无忌, password=18, address=西安), User(id=3, username=刘德华, password=26, address=苏州), User(id=4, username=郭靖, password=33, address=上海), User(id=1, username=李大锤, password=23, address=南京), User(id=3, username=带头大哥, password=36, address=杭州)]
去重后的数据：[User(id=1, username=李大锤, password=23, address=南京), User(id=2, username=张无忌, password=18, address=西安), User(id=3, username=刘德华, password=26, address=苏州), User(id=4, username=郭靖, password=33, address=上海)]

 

  // 使用Collectors.toMap去重并保持顺序
        List<Person> uniquePersons = persons.stream()
                .collect(Collectors.toMap(
                        Person::getId, // 根据id去重
                        p -> p, // 使用原始对象
                        (existing, replacement) -> existing, // 如果有重复，保留原始对象
                        LinkedHashMap::new
                )).values().stream() // 获取去重后的值
                .collect(Collectors.toList()); // 转换回List

 

  rs = new ArrayList<>(rs.stream()
                .collect(Collectors.toMap(
                        Person::getId,
                        Functions.identity(),
                        (f, n) -> f,
                        LinkedHashMap::new  
                 )).values());

 

List<Map<String, Object>> tableList

 =  tableList.stream().collect(Collectors.collectingAndThen(
                            Collectors.toMap(
                                    m -> m.get(UUID),       // key 为要比较的字段
                                    m -> m,                             // value 为 Map 本身
                                    (m1, m2) -> m1,                     // 冲突时保留第一个
                                    LinkedHashMap::new                  // 保持顺序
                            ),
                            map -> new ArrayList<>(map.values())        // 转回 List
                    ));