vending machine

class VendingMachine{
    List<Item> items = Arrays.asList(...);
    Map<Integer, ItemInfo> itemIdentifies = new HashMap<>();
    ItemInfo currentItemInfo;
    List<Coin> savings = Arrays.asList(...);
    List<Coin> currentCoins = new ArrayList<>();
    Map<ItemInfo, List<Item>> stocks;

    void selectItem(int id){
        currentItemInfo = itemIdentifies.get(id);
    }

    void insertCoins(List<Coins> coins){
        if(coins==null){return;}
        currentCoins = coins;
    }

    Item executeTrnsctn(){
        // compare price
        int sum = 0;
        for(Coin x : currentCoins){
            sum += x.getValue();
        }
        // if no sufficient, throw exception
        if(sum<currentItemInfo.getPrice()){
            throw new NoSufficientMoneyException();
        }

        // if sufficient, return back;
        Item ans = ;

        if(sum>price){
            makeRefund();
        }
    }

    List<Coin> cancelTrnsctn(){}

    void refill(List<Item>){

    }

    private List<Coin> refund(){

    }
}

class Item{
    Iteminfo iteminfo;
}

Enum ItemInfoEnum{
    CokeInfo(2.5);
    GingerInfo(3.5);

    private double price;

    ItemInfoEnum(double price){
        this.price = price;
    }

    public double getPrice(){
        return this.price;
    }

}