List去重五种方法

 转载自 : CSDN博主「Trainer2107」的原创文章

package cn.xbao;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;

public abstract class DistinctList {

    //    方法一:使用java8新特性stream进行List去重
    public static List distinct1(List<Object> list) {
        List newList = list.stream().distinct().collect(Collectors.toList());
        return newList;
    }

    //    方法二:双重for循环去重
    public static List distinct2(List<Object> list) {
        for (int i = 0; i < list.size(); i++) {
            for (int j = 0; j < list.size(); j++) {
                if (i != j && list.get(i) == list.get(j)) {
                    list.remove(list.get(j));
                }
            }
        }
        return list;
    }

    //    方法三:set集合判断去重,不打乱顺序
    public static List distinct3(List<Object> list) {
        Set set1 = new HashSet();
        List newList = new ArrayList();
        for (Object obj : list) {
            if (set1.add(obj)) {
                newList.add(obj);
            }
        }
        return newList;
    }

    //    方法四:遍历后判断赋给另一个list集合
    public static List distinct4(List<Object> list) {
        List<Object> newList = new ArrayList<>();
        for (Object obj : list) {
            if (!newList.contains(obj)) {
                newList.add(obj);
            }
        }
        return newList;
    }

    //    方法五:set和list转换去重
    public static List distinct5(List list) {
        Set set = new HashSet<>();
        List newList = new ArrayList<>();
        set.addAll(list);
        newList.add(set);
        return newList;
    }

    public static void main(String[] args) {
        List<Object> list = new ArrayList<>();
        list.add("张飞");
        list.add("刘备");
        list.add("关羽");
        list.add("刘备");
        System.out.println(list);
        List list1 = distinct1(list);
        System.out.println("java8新特性后的去重:" + list1);
        List list2 = distinct2(list);
        System.out.println("双重for循环去重:" + list2);
        List list3 = distinct3(list);
        System.out.println("set集合判断去重:" + list3);
        List list4 = distinct4(list);
        System.out.println("赋值新list去重:" + list4);
        List list5 = distinct5(list);
        System.out.println("set和list转换去重:"+ list5);
    }
}

=>运行结果 :

 

---

版权声明：本文为CSDN博主「Trainer2107」的原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/Trainer2107/article/details/78571619