// Stephen's solution

class VendingMachine {

    private int numDrPeppers, numStarbucks;
    private double amountInsertedByThisCustomer;
    private double amountInSales;

    /**
     * Create a new, fully-stocked VendingMachine object. Vending machines
     * begin with eight Dr. Peppers, six foofy Starbucks beverages, and $10 to
     * make change.
     */
    VendingMachine() {
        this.numDrPeppers = 8;
        this.numStarbucks = 6;
        this.amountInsertedByThisCustomer = 0;
        this.amountInSales = 0;
    }

    /**
     * Insert the number of dollars passed as an argument into the little coin
     * slot.
     */
    void insertMoney(double dollars) {
        this.amountInsertedByThisCustomer += dollars;
    }

    /**
     * Never mind -- gimme my money back. This method returns the amount of
     * money (in dollars) that the customer has inserted (and obviously takes
     * away their credit).
     */
    double cancel() {
        double return_value = this.amountInsertedByThisCustomer;
        this.amountInsertedByThisCustomer = 0;
        return return_value;
    }

    /**
     * Buy a Dr Pepper, and return the amount of change (in dollars) owed to
     * the customer. (Dr Peppers cost $1.25.) If there are no more Dr Peppers
     * in the machine, or if the user hasn't inserted enough money, this method
     * will throw an Exception instead of returning.
     */
    double buyDrPepper() throws Exception {
        if (this.numDrPeppers <= 0) {
            throw new Exception("No more Dr Peppers!");
        }
        if (this.amountInsertedByThisCustomer < 1.25) {
            throw new Exception("Not enough $$!");
        }
        double change = this.amountInsertedByThisCustomer - 1.25;
        this.numDrPeppers--;
        this.amountInsertedByThisCustomer = 0.0;
        this.amountInSales += 1.25;
        return change;
    }

    /**
     * Buy a foofy Starbucks beverage, and return the amount of change (in
     * dollars) owed back to the customer. (Starbucks cost $8.00.) If there are
     * no more Starbucks in the machine, or if the user hasn't inserted enough
     * money, this method will throw an Exception instead of returning.
     */
    double buyStarbucks() throws Exception {
        if (this.numStarbucks <= 0) {
            throw new Exception("No more Starbucks!");
        }
        if (this.amountInsertedByThisCustomer < 8.00) {
            throw new Exception("Not enough $$!");
        }
        double change = this.amountInsertedByThisCustomer - 8.00;
        this.numStarbucks--;
        this.amountInsertedByThisCustomer = 0.0;
        this.amountInSales += 8;
        return change;
    }

    /**
     * The vending machine man comes to refill this machine, setting it back to
     * the contents of an ordinary newly-installed machine, and collecting all
     * the big bucks it racked up from customers (in its return value).
     */
    double refill() {
        this.numDrPeppers = 8;
        this.numStarbucks = 6;
        this.amountInsertedByThisCustomer = 0;
        double amt = this.amountInSales;
        this.amountInSales = 0;
        return amt;
    }
}