out.writeObject(listTable[i].key);
            out.writeObject(listTable[i].value);
        }
    }

    @SuppressWarnings("unchecked")
    @Override
    public void readExternal(final ObjectInput in) throws IOException, ClassNotFoundException {
        final int num = in.readInt();
        mapTable = new Entry[num];
        listTable = new Entry[num];
        threshold = (int) (num * LOAD_FACTOR);

        for (Entry e = header.next; e != header; e = e.next) {
            s.writeObject(e.element);
        }
    }

    @SuppressWarnings("unchecked")
    @Override
    public void readExternal(final ObjectInput s) throws IOException, ClassNotFoundException {
        final int size = s.readInt();
        header = new Entry(null, null, null);
        header.next = header;
        header.previous = header;