从list集合中取出某一属性的值的集合案例

参考网址：https://www.jb51.net/article/193414.htm

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　　1.重要语句，输出的是list.toString()形式格式：

　　List<String> orderNoList=list.stream().map(Order::getOrderNo).collect(Collectors.toList());

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("输出单号集合："+orderNoList);
List<String> idList=list.stream().map(Order::getId()).collect(Collectors.toList());
System.out.println(idList)