public class DeReapted {

    public static void main(String[] args) {
        List<String> as = new ArrayList<>();
        as.add("a");
        as.add("e");
        as.add("f");
        as.add("a");
        as.add("d");
        as.add("f");
        System.out.println("原始数组："+as);

        //1.将list转换成set；
        List<String> res1 = new ArrayList<>();
        Set<String> set1 = new HashSet<>();
        for(String s :as){
            if(!set1.contains(s)){
                set1.add(s);
            }else {
                res1.add(s);
            }
        }
        System.out.println("方法一：将list转换成set:");
        System.out.println("去重数组set1："+set1);
        System.out.println("重复元素"+res1);
        System.out.println();

        //2.将list的contains()；
        List<String> dere = new ArrayList<>();
        List<String> res = new ArrayList<>();
        for(String s: as){
            if(!dere.contains(s)){
                dere.add(s);
            }else {
                res.add(s);
            }
        }
        System.out.println("方法二：new list加入新元素，实质还是通过contains方法对比");
        System.out.println("去重复数组dere：" +dere);
        System.out.println("不一样的元素："+res);
        System.out.println();

        //3.通过i,j两个指针循环：
        List<String> l3= new ArrayList<>();
        List<String> res2 = new ArrayList<>();
        for(int i =0;i<as.size();i++){
            for(int j=i+1;j<as.size();j++){
                if (as.get(j).equals(as.get(i))) {
                    res2.add(as.get(j));
                    as.remove(j);
                }
            }
        }
        System.out.println("方法三：双循环：");
        System.out.println("去重复数组dere："+as);
        System.out.println("不一样的元素："+res2);
        System.out.println();

        //4.利用Java8 的流：
        List ls4 = as.stream().distinct().collect(Collectors.toList());
        System.out.println("方法四：java8stream特性："+ls4);
    }
}