java8 list集合更具对象属性去重处理

话不多说直接上代码

 

package com.leinuo.jvm.list;

import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Collectors;

public class App {
    
    public static void main(String[] args) {
        listDistinct();
    }
    
    public static void listDistinct(){

        System.out.println("根据VIP order去重保留最先重复的数据-------1----2---" );
        List<VIP> collect1 = Arrays.stream(VIP.values()).collect(Collectors.toList());
        collect1 = collect1
                .stream()
                .collect(
                        Collectors.collectingAndThen(
                                Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(VIP::getOrder))),
                                ArrayList::new
                        )
                );
        System.out.println("根据VIP order去重并排序-------1-------"+collect1.toString() );

        List<VIP> collect2 = Arrays.stream(VIP.values()).collect(Collectors.toList());
        collect2 = collect2.stream().filter(distinctByKey(VIP::getOrder)).collect(Collectors.toList());
        System.out.println("根据VIP order去重并排序-------2-------"+collect2.toString() );

        System.out.println("根据VIP order去重保留最后重复的数据-------3----4---5--" );
        
        List<VIP> collect3 = Arrays.stream(VIP.values()).collect(Collectors.toList());
        Collections.reverse(collect3);
        collect3 =
                collect3
                        .stream()
                        .collect(
                                Collectors.collectingAndThen(
                                        Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(VIP::getOrder))),
                                        ArrayList::new
                                )
                        );
        System.out.println("根据VIP order去重并排序-------3-------"+collect3.toString() );

        List<VIP> collect4 = Arrays.stream(VIP.values()).collect(Collectors.toList());
        Collections.reverse(collect4);
        collect4 =
                collect4
                        .stream()
                        .filter(distinctByKey(VIP::getOrder))
                        .sorted(Comparator.comparing(VIP::getOrder))
                        .collect(Collectors.toList());
        System.out.println("根据VIP order去重并排序-------4-------"+collect4.toString() );

        List<VIP> collect5 = Arrays.stream(VIP.values()).collect(Collectors.toList());
        collect5 = collect5.stream().collect(Collectors
                .toMap(VIP -> { return VIP.getOrder();},Function.identity(), (e1, e2) -> e2))
                        .values().stream().collect(Collectors.toList());
        Collections.reverse(collect5);
        System.out.println("根据VIP order去重并排序-------5-------"+collect5.toString() );
    }

    private static <T> Predicate<T> distinctByKey(Function<? super T, Object> keyExtractor) {
        Map<Object, Boolean> seen = new ConcurrentHashMap<>();
        return t -> seen.putIfAbsent(keyExtractor.apply(t), Boolean.TRUE) == null;
    }
    
}

public enum VIP {
        VIP1(6),
        VIP2(5),
        VIP3(4),
        VIP4(2),
        VIP5(2),
        VIP6(1);


        private Integer order;

        VIP(int order) {
            this.order = order;
        }

        public Integer getOrder() {
            return order;
        }

        public void setOrder(Integer order) {
            this.order = order;
        }
}