Packages

c

o1.soda

VendingMachine

class VendingMachine extends AnyRef

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:

 INPUT: val machine = new VendingMachine(250, 10)
OUTPUT: machine: o1.soda.VendingMachine = earned 0.0 euros, inserted 0 cents, 10 bottles left

 INPUT: machine.insertMoney(300)

 INPUT: "got change: " + machine.sellBottle()
OUTPUT: res0: String = got change: 50

 INPUT: machine
OUTPUT: res1: o1.soda.VendingMachine = earned 2.5 euros, inserted 0 cents, 9 bottles left

 INPUT: machine.insertMoney(50)

 INPUT: machine.insertMoney(300)

 INPUT: machine.sellBottle()
OUTPUT: res2: Int = 100

 INPUT: machine
OUTPUT: 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.

Linear Supertypes
AnyRef, Any
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  1. VendingMachine
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Instance Constructors

  1. new VendingMachine(bottlePrice: Int, bottleCount: Int)

    bottlePrice

    the price of a single bottle

    bottleCount

    the initial number of bottles in the machine

Value Members

  1. def addBottles(newBottles: Int): Unit

    (A maintenance action:) Adds a number of bottles to the machine.

    (A maintenance action:) Adds a number of bottles to the machine. The virtual vending machine has no upper limit for bottles.

    newBottles

    the number of bottles to be added (a positive integer)

  2. var bottlePrice: Int
  3. def emptyCashbox(): Int

    (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

  4. def enoughMoneyInserted: Boolean

    Determines whether enough money has been inserted to purchase a bottle.

  5. def insertMoney(amount: Int): Unit

    (A customer action:) Adds some money towards a forthcoming purchase.

  6. def isSoldOut: Boolean

    Determines whether the machine is out of bottles.

  7. def sellBottle(): Int

    (A customer action:) Sells a bottle of virtual soda.

    (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

  8. def toString: String

    Produces a textual description of the vending machine's current state.

    Produces a textual description of the vending machine's current state.

    Definition Classes
    VendingMachine → AnyRef → Any