protected DVD() {
		this.title = "";
		this.year = 0;
		this.style = new ArrayList<Long>();
		this.amount = 0;
		this.sell = false;
		this.rent =  false;
		this.rentAmount = 0;
		this.buyPrice = 0;
		this.rentPrice = 0;
		this.sellLimit = SELL_LIMIT;
		this.rentLimit = RENT_LIMIT;
		Random r = new Random();
		this.ID = r.nextLong();
	}