public double calToCartPrice(){

double sum = 0.0;

Set<Items> keys = goods.keySet();

Iterator<Items> it = keys.iterator();

while(it.hasNext())

{

Items  i = it.next();

sum+= i.getPrice()*goods.get(i);

}

this.setTotalPrice(sum);//设置购物车总金额

return this.getTotalPrice();

}