java8從list集合中取出某一屬性的值的集合

List<Order> list = new ArrayList<User>();
        Order o1 = new Order("1","MCS-2019-1123");
        list.add(o1 );
        Order o2= new Order("2","MCS-2019-1124");
        list.add(o2);
        Order o3= new Order("3","MCS-2019-1125");
        list.add(o3);
        List<String> orderNoList=list.stream().map(Order::getOrderNo).collect(Collectors.toList());
        System.out.println("輸出單號集合："+orderNoList);
        List<String> idList=list.stream().map(Order::getId()).collect(Collectors.toList());
        System.out.println(idList)