List的五种去重方式

Posted 2020-12-25 onelikeone

//set集合去重，不改变原有的顺序
    public static void pastLeep1(List<String> list){
        System.out.println("list = [" + list.toString() + "]");
        List<String> listNew=new ArrayList<>();
        Set set=new HashSet();
        for (String str:list) {
            if(set.add(str)){
                listNew.add(str);
            }
        }
        System.out.println("listNew = [" + listNew.toString() + "]");
    }

    //遍历后判断赋给另一个list集合
    public static void pastLeep2(List<String> list){
        System.out.println("list = [" + list.toString() + "]");
        List<String> listNew=new ArrayList<>();
        for (String str:list) {
            if(!listNew.contains(str)){
                listNew.add(str);
            }
        }
        System.out.println("listNew = [" + listNew.toString() + "]");
    }

    //set去重
    public static void pastLeep3(List<String> list){
        System.out.println("list = [" + list + "]");
        Set set = new HashSet();
        List<String> listNew=new ArrayList<>();
        set.addAll(list);
        listNew.addAll(set);
        System.out.println("listNew = [" + listNew + "]");
    }

    //set去重（缩减为一行）
    public static void pastLeep4(List<String> list){
        System.out.println("list = [" + list + "]");
        List<String> listNew=new ArrayList<>(new HashSet(list));
        System.out.println("listNew = [" + listNew + "]");
    }

    //去重并按自然顺序排序
    public static void pastLeep5(List<String> list){
        System.out.println("list = [" + list + "]");
        List<String> listNew=new ArrayList<>(new TreeSet<String>(list));
        System.out.println("listNew = [" + listNew + "]");
    }