JAVA中List＜T＞中去重的几种方法

灰太狼 2022-12-29 04:47 202阅读 0赞

/** * 去重字符串重复 * @param stringList 字符串List * @return 返回去重字符串 */
        public static List<String> removeStringListDupli(List<String> stringList) { 
            Set<String> set = new LinkedHashSet<>();
            set.addAll(stringList);
            stringList.clear();
            stringList.addAll(set);
            return stringList;
        }
     
        /** * 根据对象属性去重 属性：userId * @param persons * @return */
        public static List<UserInfo> removeDupliById(List<UserInfo> persons) { 
            Set<UserInfo> personSet = new TreeSet<>((o1, o2) -> o1.getUserId().compareTo(o2.getUserId()));
            personSet.addAll(persons);
            return new ArrayList<>(personSet);
        }
     
        /** * 根据对象多个属性去重 属性：userId + userName * @param persons * @return */
        public static List<UserInfo> removeDupliByMorePro(List<UserInfo> persons){ 
            List<UserInfo> personList = persons.stream().collect(Collectors
                    .collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(o -> { 
                        // 根据useId和userName进行去重
                        return o.getUserId() + "," + o.getUsername() +"," + o.getAge();
                    }))), ArrayList::new));
            return  personList;
        }
     
        /** * 根据对象单个属性去重 属性：userId * @param persons * @return */
        public static List<UserInfo> removeDupliByUserId(List<UserInfo> persons){ 
            List<UserInfo> unique = persons.stream().collect(
                    collectingAndThen(
                            toCollection(() -> new TreeSet<>(comparingLong(UserInfo::getUserId))), ArrayList::new)
            );
            return unique;
        }
     
        /** * 根据对象单个属性去重 属性：userId * @param persons * @return */
        public static List<UserInfo> removeDupliByUserIdNew(List<UserInfo> persons){ 
     
            List<UserInfo> personList = new ArrayList<>();
             persons.stream().filter(distinctByKey(p -> p.getUserId()))
                    .forEach(p -> personList.add(p));
             return personList;
        }
     
        /** * 根据key去重重复 * @param keyExtractor key执行器 * @param <T> 泛型 * @return */
        public static <T> Predicate<T> distinctByKey(Function<? super T, Object> keyExtractor) { 
            Map<Object, Boolean> map = new ConcurrentHashMap<>();
            return t -> map.putIfAbsent(keyExtractor.apply(t), Boolean.TRUE) == null;
        }