在List by属性中查找特定对象

I have a list:

我有一个清单：

List<UserItem> userList = new ArrayList<>();

Where I add the following:

我在哪里添加以下内容：

User father = new User();
father.setName("Peter");

UserItem parent = new UserItem(father, null);
userList.add(parent);

I then create another user:

然后我创建另一个用户：

User daughter = new User();
daughter.setName("Emma");

UserItem child = new UserItem(daughter, <OBJECT IN LIST WHERE NAME IS "PETER">);
userList.add(child);

However, I need to change the text wrapped in <> above to the parent object I added before (the father), specified by the name ("Peter" in this case).

但是，我需要将上面包含的文本更改为我之前添加的父对象（父对象），由名称指定（在本例中为“Peter”）。

How can I find an object in a List by a specific attribute? In my case, how can I find the object in the List that has the name "Peter"?

如何通过特定属性在List中找到对象？在我的例子中，如何在List中找到名为“Peter”的对象？

Please note that I add hundreds, sometimes thousands, of different users like this to the list. Each "parent" has a unique name.

请注意，我在列表中添加了数百个，有时是数千个这样的不同用户。每个“父母”都有一个唯一的名称。

3 个解决方案

#1

The obvious solution would be iterating on the list and when the condition is met, return the object:

显而易见的解决方案是在列表上进行迭代，当条件满足时，返回对象：

for (User user : userList) {
    if ("peter".equals(user.getName()) {
        return user;
    }
}

And you can use filter (Java 8):

你可以使用过滤器（Java 8）：

List<User> l = list.stream()
    .filter(s -> "peter".equals(s.getUser()))
    .collect(Collectors.toList());

to get a list with all "peter" users.

获取所有“彼得”用户的列表。

As suggested in comments, I think using Map is a better option here.

正如评论中所建议的，我认为在这里使用Map是一个更好的选择。

#2

Answer to your question is here: https://*.com/a/1385698/2068880

您的问题的答案如下：https：//*.com/a/1385698/2068880

Stream peters = userList.stream().filter(p -> p.user.name.equals("Peter"))

However, as ruakh suggested, it's more reasonable to use Map<String, UserItem> to make it faster. Otherwise, it will iterate all the objects in the list to find users with name "Peter".

但是，正如Ruakh建议的那样，使用Map 来加快速度更合理。否则，它将迭代列表中的所有对象以查找名为“Peter”的用户。，useritem>

#3

Other way with parallelStream with findAny

使用findAny的parallelStream的其他方法

Optional<UserItem> optional = userList.parallelStream().findAny(p -> p.user.getName().equalsIgnoreCase("Peter"));
UserItem user = optional.isPresent() ? optional.get() : null;

#1