Java中的有序列表映射实现
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Ordered List Map implementation in Java
提问by Savvas Dalkitsis
I was wondering if there is a class out there that implements both the Mapand Listinterfaces in Java.
我想知道是否有一个类在 Java 中同时实现Map和List接口。
I have a data structure that is primarily a Map. I map strings (IDs) to Images. But in a specific part of my code, I need to present the user with all the available IDed Images. The only way to do that so far is to write this:
我有一个主要是Map. 我将字符串（ID）映射到Images。但是在我代码的特定部分，我需要向用户展示所有可用的 IDed Images。到目前为止，唯一的方法是这样写：
for (String id : myMap.keySet()) {
// get the image like this "myMap.get(id)"
}
So it would be nice to have a class that implements both Mapand Listso I could simply write:
所以如果有一个同时实现这两个类的类会很好Map，List所以我可以简单地写：
for (Image img : myMap) {
// the image is img
}
Does anyone know of such an implementation?
有谁知道这样的实现？
EDIT: After viewing the answers (which are all correct, voted up), I now realize I would also need the map to be sorted. When I say "sorted", all I mean is that I would like it to have the values in a specific order, one that I would be able to modify. I know this is not the original question, but I just realized that I need that.
编辑：查看答案（全部正确，投票通过）后，我现在意识到我还需要对地图进行排序。当我说“排序”时，我的意思是我希望它具有特定顺序的值，一个我可以修改的顺序。我知道这不是最初的问题，但我刚刚意识到我需要那个。
EDIT 2: It seems I am indecisive. What I need is an ordered map, not a sorted one. Sorry for the confusion, people.
编辑 2：看来我优柔寡断。我需要的是有序地图，而不是排序地图。对不起，人们的困惑。
采纳答案by Tadeusz Kopec
If you need your items in a specific order, LinkedHashMapis your friend - it keeps items in insertion order. TreeMap will keep your items in an order defined by either a Comparator you give or a compareTo method of the key.
如果您需要按特定顺序排列的项目，LinkedHashMap是您的朋友——它可以按插入顺序保存项目。TreeMap 将按照您提供的 Comparator 或键的 compareTo 方法定义的顺序保存您的项目。
回答by jjnguy
For an ordered Map, look at the LinkedHashMap. That will keep your keys in the order of insertion.
对于有序的 Map，请查看LinkedHashMap. 这将使您的密钥按插入顺序排列。
If you use a SortedMapit will keep the keys in sorted order. (The TreeMapis the most common implementation.)
如果您使用 a SortedMap，它将按排序顺序保存键。（这TreeMap是最常见的实现。）
What you can use is map.entrySet(). That will allow you to iterate over the Set of MapEntries.
您可以使用的是map.entrySet(). 这将允许您迭代 MapEntries 集。
Check out the javadocfor a bit more info.
查看javadoc了解更多信息。
回答by Stroboskop
This gives you a collection of the stored values
这为您提供了存储值的集合
myMap.values()
回答by akf
you can use the Map.values()method, which returns a Collection.
您可以使用该Map.values()方法，该方法返回一个Collection.
回答by Rorick
Try this:
尝试这个：
for (Image img : myMap.values()) {
// the image is img
}
For sorted map look at java.util.SortedMapimplementations. java.util.TreeMapis the most often choice. If you need just guaranteed iteration order you can try java.util.LinkedHashMap. It offers iteration in the same order as you put elements to map. Or, optionally, in last-accessed order. If you'd like to move key (once added) to the end of map, you must explicitly remove it and put again.
对于排序地图，请查看java.util.SortedMap实现。java.util.TreeMap是最常用的选择。如果您只需要保证迭代顺序，您可以尝试java.util.LinkedHashMap. 它以与将元素放入映射相同的顺序提供迭代。或者，可选地，按照最后访问的顺序。如果您想将键（一旦添加）移动到地图的末尾，您必须明确删除它并重新放置。
回答by dfa
you can use a TreeMapit is sorted according to the natural ordering of its keys, or by a Comparator provided at map creation time:
您可以使用TreeMap它根据其键的自然顺序进行排序，或者通过在地图创建时提供的 Comparator 进行排序：
TreeMap<String, Image> mapByName = new TreeMap<String, Image>(new ByNameComparator());
where ByNameComparator() is a Comparator. Alternatively you can use the values() methond and sort using Collections.sort():
其中 ByNameComparator() 是一个比较器。或者，您可以使用 values() 方法并使用 Collections.sort() 进行排序：
Collection<Image> images = mapByName.values();
Collections.sort(images, new BySizeComparator());
回答by Grzegorz Oledzki
You've got already a bunch of practical answers. But answering directly the question...
你已经得到了一堆实用的答案。但是直接回答问题...
I was wandering if there is a class out there that implements both Map and List interfaces in Java.
我在徘徊是否有一个类在 Java 中实现了 Map 和 List 接口。
... it's worth to mention that it's simply impossible. remove(Object)method is the obstacle.
…… 值得一提的是，这简直是不可能的。remove(Object)方法是障碍。
In Mapinterface its signature is:
在Map接口中，它的签名是：
V remove(Object key);
And in Listinterface it's:
在List界面中它是：
boolean remove(Object o);
