Zip two maps into a map of K to Tuple<V1, Optional<V2>>

zipit.java

/**
 * Combines two maps with the same key into a map of key to tuple(value 1, optional value 2)
 */
public static <K, V1, V2> Map<K, Tuple<V1, Optional<V2>>> 
    zip(Map<K, V1> map1, Map<K, V2> map2)
{
    Map<K, Tuple<V1, Optional<V2>>> results = new HashMap<>();
    for (K key : map1.keySet())
    {
        V1 val1 = map1.get(key);
        Optional<V2> val2 = Optional.fromNullable(map2.get(key));
        results.put(key, Tuple.from(val1, val2));
    }
    return results;         
}