Java key - key map

Question

I need a kind of map which is accessible in two directions, so with a key-key structure instead of key-value. Does this exist in Java? If not, what is the best way to create it?

So example:

mySpecialHashMap.put("key1", "key2");

mySpecialMap.getL2R("key1") returns "key2";
mySpecialMap.getR2L("key2") returns "key1";

Dupe: http://stackoverflow.com/questions/1670038/does-java-have-a-hashmap-with-reverse-lookup — finnw, Nov 05 '09 at 17:50

score 23 · Accepted Answer · edited Jan 29 '18 at 10:22

23

So you want a bidirectional map. You can use Apache Commons Collections BidiMap or Google Collections BiMap for this.

edited Jan 29 '18 at 10:22

agilob

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answered Nov 05 '09 at 13:12

BalusC

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Jonik · Answer 2 · 2011-12-20T17:22:35.160

3

You might want to look at BiMap from the Guava library (formerly known as Google Collections).

An example where a HashBiMap is used as the "mySpecialHashMap":

BiMap<String, String> myBiMap = HashBiMap.create();
myBiMap.put("key1", "key2");

myBiMap.get("key1"); // returns "key2"
myBiMap.inverse().get("key2"); // returns "key1"

edited Dec 20 '11 at 17:22

answered Nov 05 '09 at 13:12

Jonik

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If someone's not using Guava yet: it's totally sweet and you probably should. See [this post (and comments)](http://stackoverflow.com/a/132639/56285) for some great learning resources. – Jonik Dec 20 '11 at 17:25

score 2 · Answer 3 · answered Nov 05 '09 at 13:11

2

Yes, there is BiMap from Google Collections.

answered Nov 05 '09 at 13:11

luvieere

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score 1 · Answer 4 · edited May 23 '17 at 10:25

1

Or for reversible enums see this Stackoverflow question.

edited May 23 '17 at 10:25

Community

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answered Nov 05 '09 at 13:13

C. Ross

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Java key - key map

4 Answers4

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