java Java8 将对象列表转换为对象的一个属性列表
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Java8 Transform list of object to list of one attribute of object
提问by Nik
I want to use Java 8 tricks to do the following in one line.
我想使用 Java 8 技巧在一行中执行以下操作。
Given this object definition:
鉴于此对象定义：
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class MyObj {
private String id;
private Double value;
}
and a List<MyObj> objects, I want to get a List<String> objectIdswhich is a list of all ids of the objects in the first list - in the same order.
和 a List<MyObj> objects，我想得到 a List<String> objectIds，它是第一个列表中所有id对象的列表 - 以相同的顺序。
I can do this using a loop in Java but I believe there should be a one-liner lambda in Java8 that can do this. I was not able to find a solution online. Perhaps I wasn't using the right search terms.
我可以使用 Java 中的循环来做到这一点，但我相信 Java8 中应该有一个单行 lambda 可以做到这一点。我无法在网上找到解决方案。也许我没有使用正确的搜索词。
Could someone suggest a lambda or another one-liner for this transform?
有人可以为这个转换建议一个 lambda 或另一个单行吗？
回答by xiumeteo
This should do the trick:
这应该可以解决问题：
objects.stream().map(MyObj::getId).collect(Collectors.toList());
objects.stream().map(MyObj::getId).collect(Collectors.toList());
that said, the method reference::operator allows you to reference any method in your classpath and use it as a lambda for the operation that you need.
也就是说，方法引用::运算符允许您引用类路径中的任何方法，并将其用作所需操作的 lambda。
As mentioned in the comments, a stream preserves order.
正如评论中提到的，流会保留顺序。
