List Set Map的添加和打印格式比较

List Set Map的添加和打印格式比较

public static void main(String[] args) {
        ArrayList<Object> objects = new ArrayList<>();
        objects.add(new User(5L,"aaaa","ddd"));
        objects.add(new User(7L,"aaaa1","ddd1"));
        System.out.println("List集合"+objects);
        HashMap<String , Object> objectObjectHashMap = new HashMap<>();
        objectObjectHashMap.put("meg",new User(6L,"bbbb","cccc"));
        objectObjectHashMap.put("meg1",new User(6L,"bbbb","cccc"));
        System.out.println("map集合"+objectObjectHashMap);
        Set<Object> objects1 = new HashSet<>();
        objects1.add(new User(5L,"aaaa","ddd"));
        objects1.add(new User(51L,"aaaa1","ddd1"));
        System.out.println("set集合"+objects1);
    }

注：List 和Set 打印结果一样（只不过是一个有序，一个无序），map是键值对的形式