public void decrease(int amount) throws NotEnoughMoneyException {
        int walletMoney = this.wallet.getAmountOfMoney();
        if(walletMoney < amount)
            throw new NotEnoughMoneyException();
        else if(walletMoney == amount)
            this.wallet.updateState(new EmptyState(this.wallet));
        else
            this.wallet.safeDecrease(amount);
    }