Bidirectional Map

Can you suggest a kind of map or similar data structure where we can get both the value and key from each other at equal ease. That is to say, that each may be used to find other.

Java doesn't have a bidirectional map in its standard library.

Use for example BiMap<K, V> from Google Guava .

If you feel it pain importing some third party library. How about this simple class.

public class BiMap<K,V> {

    HashMap<K,V> map = new HashMap<K, V>();
    HashMap<V,K> inversedMap = new HashMap<V, K>();

    void put(K k, V v) {
        map.put(k, v);
        inversedMap.put(v, k);
    }

    V get(K k) {
        return map.get(k);
    }

    K getKey(V v) {
        return inversedMap.get(v);
    }

}

Make sure K and V class has proper hashCode implementation.