将对象流转换为链接的属性列表 [英] Turn a stream of objects into a linked list of attributes

问题描述

我的目标：获取 LinkedList 用户并提取 LinkedList 他们的用户名以优雅的Java-8方式。

My goal: Take a LinkedList of Users and extract a LinkedList of their usernames in an elegant, Java-8 way.

public static void main(String[] args) {

    LinkedList<User> users = new LinkedList<>();
    users.add(new User(1, "User1"));
    users.add(new User(2, "User2"));
    users.add(new User(3, "User3"));

    // Vanilla Java approach
    LinkedList<String> usernames = new LinkedList<>();
    for(User user : users) {
        System.out.println(user.getUsername());
        usernames.add(user.getUsername());
    }
    System.out.println("Usernames = " + usernames.toString());

    // Java 8 approach
    users.forEach((user) -> System.out.println(user.getUsername()));
    LinkedList<String> usernames2 = users.stream().map(User::getUsername). // Is there a way to turn this map into a LinkedList?
    System.out.println("Usernames = " + usernames2.toString());
}

static class User {
    int id;
    String username;

    public User() {
    }

    public User(int id, String username) {
        this.id = id;
        this.username = username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public int getId() {
        return id;
    }
}

我试图转换将对象转换为 LinkedList 。我可以将它变成一个数组（ Stream :: toArray（））并将其转换为 List （ Arrays.asList（Stream :: toArray（）））但看起来就是这样......不，谢谢。

I am stuck trying to convert the Stream object into a LinkedList. I could turn it into an array (Stream::toArray()) and turn that into a List (Arrays.asList(Stream::toArray())) but that just seems so... no thank you.

我错过了什么吗？

推荐答案

您可以像这样使用收藏家将结果放入 LinkedList ：

You can use a Collector like this to put the result into a LinkedList:

LinkedList<String> usernames2 = users.stream()
                                .map(User::getUsername)
                                .collect(Collectors.toCollection(LinkedList::new));

这篇关于将对象流转换为链接的属性列表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！