Best Java Datastructure to store key Value Pair

Question

Possible Duplicate:
Java Hashmap: How to get key from value?
Bi-directional Map in Java?

I want a key value data structure to use for Android App. I can use Map<K,V>, but in Map I can't get key for particular Value.

Is there any good Java data structure using which I can retrieve key by value and vice-versa.

Look at Guava's [BiMap](http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/collect/BiMap.html) — jlordo, Jan 30 '13 at 09:43
You could just implement a small method to do so; it will be 4 lines of code; instead of using any third party. — Deepak Singhal, Jan 30 '13 at 09:45
@Deepak it is better to use well-tested and widely accepted libraries for such a general use case. You will avoid a lot of pain. — autra, Jan 30 '13 at 09:47
Exact duplicate of http://stackoverflow.com/questions/10699492/bi-directional-map-in-java and http://stackoverflow.com/questions/1670038/does-java-have-a-hashmap-with-reverse-lookup — autra, Jan 30 '13 at 09:48
Second answer on http://stackoverflow.com/questions/1383797/java-hashmap-how-to-get-key-from-value — Deepak Singhal, Jan 30 '13 at 09:49

score 19 · Accepted Answer · edited May 29 '14 at 12:25

19

You can use Map with entrySet and Map.Entry class to iterate and get both keys and values even if you don't know any of the keys in the Map.

Map <Integer,String> myMap = new HashMap<Integer,String>();

Iterator<Entry<Integer, String>> iterator = myMap.entrySet().iterator();
while (iterator.hasNext()) {
    Map.Entry<Integer,String> pairs = (Map.Entry<Integer,String>)iterator.next();
    String value =  pairs.getValue();
    Integer key = pairs.getKey();
    System.out.println(key +"--->"+value);
}

edited May 29 '14 at 12:25

Wesley Womack

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answered Jan 30 '13 at 09:59

Saumik Chaurasia

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Sure, this will work. But it will be slower and slower with growing number of entries. He's better of with a `BiMap` – jlordo Jan 30 '13 at 10:07
1

But He need not to put a new jar file and make his app heavy, And I don't find any much significant change in performance. – Saumik Chaurasia Jan 30 '13 at 10:17
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Do you prefer an app that get's slower over time, or an app that is (a tiny little bit) bigger when downloading initially? – jlordo Jan 30 '13 at 10:19
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Depends... Also bi map will maintain two maps and internally and not allow me to duplicate value – Saumik Chaurasia Jan 30 '13 at 10:30
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which makes total sense: If you had duplicate values, which key would you choose for an inverse lookup?? That's what OP is trying to do. – jlordo Jan 30 '13 at 10:33

score 1 · Answer 2 · edited May 23 '17 at 12:32

1

Use Google Guava BiMap

How to use Guava Libraris in Android is here

edited May 23 '17 at 12:32

Community

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answered Jan 30 '13 at 09:52

TheWhiteRabbit

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Robin Mukanganise · Answer 3 · 2014-08-22T08:34:01.927

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The best data structure would be Java HashMaps check this link you can use the get(Object key) method

edited Aug 22 '14 at 08:34

answered Jan 30 '13 at 10:12

Robin Mukanganise

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Best Java Datastructure to store key Value Pair

3 Answers3