Two Way Mapping using single Data Structure

Question

I ran across some code recently at work (recreated to be similar to what I am dealing with) similar to the code below

Is there a way I can rework the code below to use one data structure (with performance in mind)?

Here is some code to illustrate what I mean:

public class ObjectMapper {

    private Map<UUID,Integer> uuidMap;
    private Map<Integer,UUID> indexMap;

    public ObjectMapper(){
     uuidMap = new HashMap<UUID,Integer>();
     indexMap = new HashMap<Integer,UUID>();
    }

    public void addMapping(int index, UUID uuid){
     uuidMap.put(uuid, index);
     indexMap.put(index, uuid);
    }


    .
    .
    .

    public Integer getIndexByUUID(UUID uuid){
     return uuidMap.get(uuid);
    }

    public UUID getUUIDByIndex(Integer index){
     return indexMap.get(index);
    }


}

Answer 1

This is answered here with the recommendation to use BitMap from Google Collections

Answer 2

You could use a single Map<Object,Object> to do both mappings. Ugly, sure. Performance should be roughly the same, or slightly better in the unlikely event that you have many ObjectMappers with few mapped values.

Answer 3

Apache collections supports a BidiMap interface and a variety of fairly effective implementations.