List<T> list对象去重方法总结

Love The Way You Lie 2021-12-13 12:53 535阅读 0赞

> ### List<T> list对象去重方法总结 ###

** 【去重方法总结】：（java8）**

package com.caox.utils;
    
    import com.caox.model.UserInfo;
    
    import java.util.*;
    import java.util.concurrent.ConcurrentHashMap;
    import java.util.function.Function;
    import java.util.function.Predicate;
    import java.util.stream.Collectors;
    
    import static java.util.Comparator.comparingLong;
    import static java.util.stream.Collectors.collectingAndThen;
    import static java.util.stream.Collectors.toCollection;
    
    /**
     * @author : nazi
     * @version : 1.0
     * @date : 2019/7/5 17:54
     * 去重List<对象>
     */
    public class ListObjectNoRepeatUtils {
    
    
        /**
         * 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;
        }
    
    }

**【对应实体类】： **

package com.caox.model;
    
    import lombok.Data;
    
    import java.text.SimpleDateFormat;
    import java.util.Date;
    
    /**
     * @author : nazi
     * @version : 1.0
     * @date : 2019/6/5 14:27
     */
    @Data
    public class UserInfo {
    
        private Integer userId;
        private String username;
        private Date birthDate;
        private Integer age;
        private float fRate;
        private char ch;
    
        public Date getBirthDate() {
            return birthDate;
        }
    
        public String getBirthDatestr() {
            SimpleDateFormat formater = new SimpleDateFormat("yyyy-MM-dd");
            return formater.format(getBirthDate());
        }
    
        public UserInfo(Integer userId, String username, Date birthDate, Integer age, float fRate, char ch) {
            this.userId = userId;
            this.username = username;
            this.birthDate = birthDate;
            this.age = age;
            this.fRate = fRate;
            this.ch = ch;
        }
    
        public UserInfo(Integer userId, String username) {
            this.userId = userId;
            this.username = username;
        }
    
        public UserInfo(Integer userId, String username, Integer age) {
            this.userId = userId;
            this.username = username;
            this.age = age;
        }
    
        @Override
        public String toString() {
            return "UserInfo{" +
                    "userId=" + userId +
                    ", username='" + username + '\'' +
                    ", birthDate=" + birthDate +
                    ", age=" + age +
                    ", fRate=" + fRate +
                    ", ch=" + ch +
                    '}';
        }
    
        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
    
            UserInfo userInfo = (UserInfo) o;
    
            if (!userId.equals(userInfo.userId)) return false;
            return username.equals(userInfo.username);
    
        }
    
        @Override
        public int hashCode() {
            int result = userId.hashCode();
            result = 31 * result + username.hashCode();
            return result;
        }
    }