VendingMachine
The class VendingMachine can be used to simulate simple virtual soda vending
machines. A vending machine sells bottles of a single type of soft drink at a
certain price per bottle.
The methods of the class correspond to the actions of buyers and maintenance
personnel on an actual vending machine. For instance, a purchase is made by
first inserting some money possibly several times with each one adding to the
previous insertion, and then selecting to buy a bottle. This interaction is
captured by the methods insertMoney and buyBottle.
Some of the methods are illustrated in the following REPL session, in which the vending machine initially contains 10 bottles with a price of 250 cents (2.5 euros) each:
scala> val machine = VendingMachine(250, 10)
machine: o1.soda.VendingMachine = earned 0.0 euros, inserted 0 cents, 10 bottles left
scala> machine.insertMoney(300)
scala> "got change: " + machine.sellBottle()
val res0: String = got change: 50
scala> machine
val res1: o1.soda.VendingMachine = earned 2.5 euros, inserted 0 cents, 9 bottles left
scala> machine.insertMoney(50)
scala> machine.insertMoney(300)
scala> machine.sellBottle()
val res2: Int = 100
scala> machine
val res3: o1.soda.VendingMachine = earned 5.0 euros, inserted 0 cents, 8 bottles left
As the example illustrates, a vending machine object has a mutable state: it keeps track of how much money the user has inserted, for instance. The machine also tracks the number of bottles it contains, the current (modifiable) price per bottle, and the money it has “earned” by selling bottles.
- Value parameters:
- bottleCount
the initial number of bottles in the machine
- bottlePrice
the price of a single bottle
Value members
Concrete methods
(A maintenance action:) Adds a number of bottles to the machine. The virtual vending machine has no upper limit for bottles.
(A maintenance action:) Adds a number of bottles to the machine. The virtual vending machine has no upper limit for bottles.
- Value parameters:
- newBottles
the number of bottles to be added (a positive integer)
(A maintenance action:) Removes all the earned cash from the machine.
(A maintenance action:) Removes all the earned cash from the machine.
- Returns:
the amount of money previously earned by the machine through sales
Determines whether enough money has been inserted to purchase a bottle.
Determines whether enough money has been inserted to purchase a bottle.
(A customer action:) Adds some money towards a forthcoming purchase.
(A customer action:) Adds some money towards a forthcoming purchase.
(A customer action:) Sells a bottle of virtual soda. This can only be done, however, if enough money has been inserted and there are bottles left in the machine. If the sale was successful, the method adds the earnings in the machine’s cashbox, removes a single bottle, and sets up for the next transaction by resetting the amount of inserted cash to zero.
(A customer action:) Sells a bottle of virtual soda. This can only be done, however, if enough money has been inserted and there are bottles left in the machine. If the sale was successful, the method adds the earnings in the machine’s cashbox, removes a single bottle, and sets up for the next transaction by resetting the amount of inserted cash to zero.
- Returns:
the amount of money (0 or more) given to the buyer as change, or a negative value to signal an unsuccessful purchase