ArrayList去除重复元素（多种方法实现）

package other;

import java.util.ArrayList;

import java.util.HashSet;

public class test4 {

    public static void main(String[] args) {

        ArrayList list = new ArrayList();

        list.add("aaa");

        list.add("aaa");

        list.add("bbb");

        list.add("bbb");

        list.add("ccc");

        list.add("ccc");

        list.add("ccc");

        //双重循环去重

       System.out.println( removeDuplicate_3(list));

    }

    //1.循环list中所有的元素然后删除

    public static ArrayList removeDuplicate_1(ArrayList list){

        for(int i =0;i<list.size()-1;i++){

            for(int j=list.size()-1;j>i;j--){

                if(list.get(i).equals(list.get(j)))

                    list.remove(j);

            }

        }

        return list;

    }

    //2.利用hashSet剔除重复元素,但是是无序的

    public static ArrayList removeDuplicate_2(ArrayList list){

        HashSet set = new HashSet(list);

        //使用LinkedHashSet可以保证输入的顺序

        //LinkedHashSet<String> set2 = new LinkedHashSet<String>(list);

        list.clear();

        list.addAll(set);

        return list;

    }

    //3.利用list的contains方法去重

    public static ArrayList removeDuplicate_3(ArrayList list){

        ArrayList tempList = new ArrayList(list.size());

        for(int i=0;i<list.size();i++){

            if(!tempList.contains(list.get(i)))

                tempList.add(list.get(i));

        }

        return tempList;

    }

}

其他优雅方法去除重复元素：

https://blog.csdn.net/caoxiaohong1005/article/details/54286384