Question

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Any implementation of Map<K1, K2, V>, i.e. two keys?

I need to store name and id as key value pair. However I need to look up by both name and id at times in my program. I don’t want to create two HashMap (or double the memory consumption by storing name-id and id-name pair)

What is a suitable data structure for it? Is there a Standard implementation in java for this?

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.