@Override
    public String toString() {
        if(this.size() == 0) {
            return "[]";
        }
        StringBuilder s = new StringBuilder();
        s.append("[");
        for(LinkedList<E> bucket : buckets) {
            if(bucket != null) {
                for(E e : bucket) {
                    s.append(String.valueOf(e) + " ");
                }
            }
        }
        s.replace(s.length() - 1, s.length(), "]");
        return s.toString();
    }