是否有一个保留插入顺序的 Set 也实现了 List? [英] Is there an insertion order preserving Set that also implements List?

问题描述

我正在尝试在 Java 中同时找到 java.util.List 和 java.util.Set 的实现.我希望这个类只允许唯一的元素(如 Set)并保留它们的顺序(如 List).它存在于 JDK 6 中吗?

I'm trying to find an implementation of java.util.List and java.util.Set at the same time in Java. I want this class to allow only unique elements (as Set) and preserve their order (like List). Does it exist in JDK 6?

List#add(int, T) 很重要，这样我就可以插入到特定位置.

It's important to have List<T>#add(int, T) so I can insert into a specific position.

推荐答案

TreeSet 按元素顺序排序；LinkedHashSet 保留插入顺序.希望其中之一是您所追求的.

TreeSet is sorted by element order; LinkedHashSet retains insertion order. Hopefully one of those is what you were after.

您已指定要能够在任意位置插入，我怀疑您必须自己编写 - 只需创建一个包含 HashSet 的类; 和一个 ArrayList;添加项目时，先检查它是否在集合中，然后再添加到列表中.

You've specified that you want to be able to insert at an arbitrary location, I suspect you'll have to write your own - just create a class containing a HashSet<T> and an ArrayList<T>; when adding an item, check whether or not it's in the set before adding it to the list.

或者 Apache 的 commons-collections4 提供 ListOrderedSet 和 SetUniqueList，它们的行为类似并且应该满足给定的要求.

Alternatively Apache's commons-collections4 offers ListOrderedSet and SetUniqueList, which behave similarly and should meet the given requirements.

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