Java List 去重

import java.util.*;
import java.util.stream.Collectors;

public class QuChong {
    public static void main(String[] args) {

        List<Integer> list = new ArrayList<>();
        list.add(1);
        list.add(1);
        list.add(3);
        list.add(1);
        list.add(12);
        list.add(1);
        list.add(3);
        list.add(3);


        removeDuplicate(list);
        List a = removeDuplicateFromJava8(list);
        removeDuplicateByContains(list);
        List a = removeDuplicateHashSet(list);
        System.out.println( "result:"+ a);
    }

    //1.Java8 新特性
    public static List removeDuplicateFromJava8(List list){

        List list1=(List) list.stream().distinct().collect(Collectors.toList());
        return list1;

    }

    //2.循环list中的所有元素然后删除重复
    public static List removeDuplicate(List list){
        for (int i = 0; i < list.size() - 1; i++){
            for (int j = list.size() - 1; j > i; j--){
                if(list.get(j).equals(list.get(i))){
                    list.remove(j);
                }
            }
        }
        System.out.println("removeDuplicate" + list);
        return list;
    }
    //把list里的对象遍历一遍，用list.contains(),如果不存在就放入到另一个list集合中
    public static List removeDuplicateByContains(List list){
        List listTemp = new ArrayList();
        for(int i=0;i<list.size();i++){
            if(!listTemp.contains(list.get(i))){
                listTemp.add(list.get(i));
            }
        }
        System.out.println("removeDuplicateByContains" + listTemp);
        return listTemp;

    }

// 通过HashSet踢除重复元素
    public static List removeDuplicateHashSet(List list) {
        HashSet h = new HashSet(list);
        list.clear();
        list.addAll(h);
        return list;
    }



}