java - 双重查找地图

Question

可能重复：
Map<K1, K2, V> 的任何实现，即两个键？

我需要将名称和 ID 存储为键值对。但是，我有时需要在我的程序中同时按名称和 ID 进行查找。我不想创建两个 HashMap（或者通过存储 name-id 和 id-name 对来增加内存消耗）

什么是适合它的数据结构？java中是否有为此的标准实现？

Answer 1

You can use also guava's BiMap. And to get the inverse map is as simple as:

BiMap<Integer, String> biMap = HashBiMap.create();
biMap.put(1, "a");
biMap.put(2, "b");
BiMap<String, Integer> invertedMap = biMap.inverse(); //to get the name,id map

The only constraint is that your keys and values should be unique.

Answer 2

Guava has HashBiMap which keeps track of both directions of a mapping for you. Currently, its implementation basically just maintains a HashMap in each direction, but the next release will use a custom data structure saving something like ~38% on memory.

Essentially, HashBiMap behaves exactly like a Map, except that it rejects duplicate values, and you can get a view of the other direction -- values to keys -- by calling inverse().

(Disclosure: I contribute to Guava.)

Answer 3

Commons-Collections 有您可以使用的 BidiMap：

http://commons.apache.org/collections/apidocs/org/apache/commons/collections/BidiMap.html