@Override
    public int hashCode() {
        int h = 0;
        for (int i = 0; i < used; i++) {
            h += key(i).hashCode();
            V v = value(i);
            if (v != null) {
                h += v.hashCode();
            }
        }
        return h;
    }
Finds the index where the key,value pair is stored.
@param key to look for
@return the index where the key is found or -1 if it is not found
vespajlib/src/main/java/com/yahoo/collections/Hashlet.java