/**
         * Copy constructor.
         * @param source map to copy
         */
        public OpenIntToDoubleHashMap(OpenIntToDoubleHashMap source)
        {
            int length = source.keys.Length;

            keys = new int[length];
            Array.Copy(source.keys, 0, keys, 0, length);
            values = new double[length];
            Array.Copy(source.values, 0, values, 0, length);
            states = new byte[length];
            Array.Copy(source.states, 0, states, 0, length);
            missingEntries = source.missingEntries;
            _size          = source._size;
            mask           = source.mask;
            count          = source.count;
        }
 public Iterator(OpenIntToDoubleHashMap parent)
 {
     _parent = parent;
 }