[AdamSpeight2008]

Back from the Hiatus. Bring on the challenge.

Challenge: Change Machine

Challenge:

Write a class that simulates the functionality of a change machine.

Requirements:-

• A Constructor that accepts a list of coins.
  So you can setup the initial state of the machine. What denominations it accepts and initial quantities. etc.
  
• A way to set the Unit Price.
  Edit: Unit Price -> The amount you have to pay, before goods are dispensed and change issued.
  
• A way of inserting coins
  
• A way to return the coins the user has inserted for the current transaction.
  
• A way to dispense the change (once the unit price is met), made from the available coins in the machine.
  Excluding those the user has insert for the current transaction. After the transaction is completer those coins are available to be used for change.
  
• Raise Events to reflect the internal state changes.

Submissions (preferably vb.net) must follow the traditional challenge standing orders.

This post has been edited by AdamSpeight2008: 02 October 2012 - 08:58 AM

[modi123_1]

Quote

A way to set the Unit Price.

What do you mean by this?

[AdamSpeight2008]

Unit Price -> The amount you have to pay, before goods are dispensed and change issued.

[modi123_1]

Ah... okay I thought this was just a change machine as in it took larger denominations and dispensed said denomination broken down into smaller change... not like a vending machine.

Well poop. That alters things.

[AdamSpeight2008]

Could be either, depends on how you configure the change mechanism algorithm.
Hence the events requirements.

Coin Dispenser
Set Unit Price to equal value of coin inserted.
Dispense coins

Change Giver
Set Unit Price to equal value of purchases
Insert coins
Dispense change.

Separation of functionality. Change Mechanism != Vending Machine.

This post has been edited by AdamSpeight2008: 02 October 2012 - 09:16 AM

[modi123_1]

Hrm... okay.

[lucky3]

I'm submitting 75% done solution. I need to work on possible logical errors, and implement PurchaseGoods() method. I need to modify FindCoinsToBreak() so it will look first if it has sufficient coins, then modify state in containers (minor fix). Here and there I repeat some code, so I'll need to encapsulate it later, etc...It's spaghetti code, but will polish it. I'll continue with this in a day or two, because there's much work waiting for me See you later.

Spoiler

ChangeMachine:

Spoiler

Imports System.Linq

Public Class ChangeMachine
#Region "Properties"
    Private Property _goodsContainerMaximum As Integer
    Public ReadOnly Property GoodsContainerMaximum As Integer
        Get
            Return _goodsContainerMaximum
        End Get
    End Property

    Private Property _coinContainerMaximum As Integer
    Public ReadOnly Property CoinContainerMaximum As Integer
        Get
            Return _coinContainerMaximum
        End Get
    End Property

    Private Property _stateOfCoins As List(Of PackOfCoins)
    Public ReadOnly Property StateOfCoins As List(Of PackOfCoins)
        Get
            Return _stateOfCoins
        End Get
    End Property

    Private Property _stateOfGoods As List(Of PackOfGoods)
    Public ReadOnly Property StateOfGoods As List(Of PackOfGoods)
        Get
            Return _stateOfGoods
        End Get
    End Property

    Private Property _machineName As String
    Public ReadOnly Property Name As String
        Get
            Return _machineName
        End Get
    End Property


#End Region

#Region "Public methods"
    'constructor: initialy I fill it only with coins, because the challenge says it's change machine, 
    'and I can add goods later
    Public Sub New(ByVal InitialCoinList As List(Of PackOfCoins),
                   ByVal MachineName As String,
                   ByVal EachCoinContainerMaximum As Integer,
                   ByVal EachGoodsContainerMaximum As Integer)

        _goodsContainerMaximum = EachGoodsContainerMaximum
        _coinContainerMaximum = EachCoinContainerMaximum
        _stateOfCoins = InitialCoinList
        _machineName = MachineName
        _stateOfGoods = New List(Of PackOfGoods)
    End Sub

    Public Sub RefillCoins(ByVal coinList As List(Of PackOfCoins))
        REM would be smart to set maximum coin limit
        Dim myListOfCoins As New List(Of PackOfCoins)
        myListOfCoins = FillCoinsAndReturnExcesiveCoins(coinList)
        RaiseEvent CoinSupplyFiled(Me, "Coins added", myListOfCoins)
    End Sub

    Public Sub AddGoods(ByVal goodsToAdd As List(Of PackOfGoods))
        REM check for allowed quantity
        Dim myListOfGoods As New List(Of PackOfGoods)
        myListOfGoods = FillGoodsAndReturnExcesiveGoods(goodsToAdd)
        RaiseEvent GoodsAdded(Me, "Goods added!", myListOfGoods)
    End Sub

    ''' <summary>
    ''' Breaks paper money and coins to change
    ''' </summary>
    ''' <param name="coinList">could be coins or paper money</param>
    ''' <remarks></remarks>
    Public Sub ChangeCoins(ByVal coinList As List(Of PackOfCoins))
        REM will consider 2 as maximum value of coin, the rest is paper money
        Dim returnList As New List(Of List(Of PackOfCoins))
        'sort coins descending by denominations
        SortCoins(coinList)
        For Each item In coinList

            'break it down

            'will simply start with highest denomination and move down
            For n = 0 To item.Quantity - 1
                returnList.Add(FindCoinsToBreak(item.WhatCoin.Denomination))
            Next


        Next
        RaiseEvent CoinsChanged(Me, "Coins changed!", returnList)
    End Sub

    Public Sub PurchaseGoods()
        'todo: implement PurchaseGoods method
    End Sub

#End Region

#Region "Public events"
    Public Event CoinSupplyFiled(ByRef sender As ChangeMachine, ByVal message As String, ByVal returnedCoins As List(Of PackOfCoins))
    Public Event GoodsAdded(ByRef sender As ChangeMachine, ByVal message As String, ByVal returnedGoods As List(Of PackOfGoods))
    Public Event NoMoreCoinsInMachine(ByRef sender As ChangeMachine, ByVal message As String)
    Public Event CoinsChanged(ByRef sender As ChangeMachine, ByVal message As String, ByVal returnedCoins As List(Of List(Of PackOfCoins)))
#End Region

#Region "Private methods"
    Private Function FillCoinsAndReturnExcesiveCoins(ByVal coins As List(Of PackOfCoins)) As List(Of PackOfCoins)

        Dim returnList As New List(Of PackOfCoins)
        For Each item In coins
            Dim _item = item
            Dim coinResults = From thisCoins In _stateOfCoins
                              Where thisCoins.WhatCoin.Denomination = _item.WhatCoin.Denomination AndAlso thisCoins.Quantity < _coinContainerMaximum


            If coinResults.ToList.Count > 0 Then
                'I have this type of coin already

                Dim coinDifferenceMax As Integer = _coinContainerMaximum - _stateOfCoins.Find(Function(c) _item.WhatCoin.Denomination = c.WhatCoin.Denomination).Quantity
                Dim quantityOfCoinsToAdd As Integer
                Dim remainingCoins As Integer

                If _item.Quantity < coinDifferenceMax Then
                    quantityOfCoinsToAdd = _item.Quantity
                Else
                    quantityOfCoinsToAdd = item.Quantity - (_item.Quantity - coinDifferenceMax)
                    remainingCoins = _item.Quantity - quantityOfCoinsToAdd
                End If

                _stateOfCoins.Find(Function(c) _item.WhatCoin.Denomination = c.WhatCoin.Denomination).Quantity += quantityOfCoinsToAdd
                _item.Quantity = remainingCoins
                If _item.Quantity > 0 Then
                    returnList.Add(_item)
                End If
            Else
                'new coin value type
                Dim coinDifferenceMax As Integer = _coinContainerMaximum
                Dim quantityOfCoinsToAdd As Integer
                Dim remainingCoins As Integer

                If _item.Quantity < coinDifferenceMax Then
                    quantityOfCoinsToAdd = _item.Quantity
                Else
                    quantityOfCoinsToAdd = item.Quantity - (_item.Quantity - coinDifferenceMax)
                    remainingCoins = _item.Quantity - quantityOfCoinsToAdd
                End If


                _item.Quantity = quantityOfCoinsToAdd
                _stateOfCoins.Add(_item)
                If remainingCoins > 0 Then
                    Dim returnItem As New PackOfCoins(_item.WhatCoin, remainingCoins)
                    returnList.Add(returnItem)
                End If
            End If

        Next
        Return returnList
    End Function

    Private Function FillGoodsAndReturnExcesiveGoods(ByVal goods As List(Of PackOfGoods)) As List(Of PackOfGoods)

        Dim returnList As New List(Of PackOfGoods)
        For Each item In goods
            Dim _item = item
            Dim goodsResults = From thisGoods In _stateOfGoods
                              Where thisGoods.WhatGoods.Name = _item.WhatGoods.Name AndAlso thisGoods.Quantity < _goodsContainerMaximum


            If goodsResults.ToList.Count > 0 Then
                Dim goodsDifference As Integer = _goodsContainerMaximum - _stateOfGoods.Find(Function(c) _item.WhatGoods.Name = c.WhatGoods.Name).Quantity
                Dim quantityOfGoodsToAdd As Integer
                Dim remainingGoods As Integer

                If _item.Quantity < goodsDifference Then
                    quantityOfGoodsToAdd = _item.Quantity
                Else
                    quantityOfGoodsToAdd = item.Quantity - (_item.Quantity - goodsDifference)
                    remainingGoods = _item.Quantity - quantityOfGoodsToAdd
                End If

                _stateOfGoods.Find(Function(c) _item.WhatGoods.Name = c.WhatGoods.Name).Quantity += quantityOfGoodsToAdd
                _item.Quantity = remainingGoods
                If _item.Quantity > 0 Then
                    returnList.Add(_item)
                End If
            Else
                'new coin value type
                Dim goodsDifference As Integer = _goodsContainerMaximum
                Dim quantityOfGoodsToAdd As Integer
                Dim remainingGoods As Integer

                If _item.Quantity < goodsDifference Then
                    quantityOfGoodsToAdd = _item.Quantity
                Else
                    quantityOfGoodsToAdd = item.Quantity - (_item.Quantity - goodsDifference)
                    remainingGoods = _item.Quantity - quantityOfGoodsToAdd
                End If


                _item.Quantity = quantityOfGoodsToAdd
                _stateOfGoods.Add(_item)
                If remainingGoods > 0 Then
                    Dim returnItem As New PackOfGoods(_item.WhatGoods, remainingGoods)
                    returnList.Add(returnItem)
                End If
            End If
        Next

        Return returnList
    End Function

    Private Function FindCoinsToBreak(ByVal valueOfMoneyToBreak As Decimal) As List(Of PackOfCoins)
        Dim returnList As New List(Of PackOfCoins)

        Dim listOfCoinsWithDenomination = From coins In _stateOfCoins
                                          Where coins.WhatCoin.Denomination <= 2 AndAlso coins.Quantity > 0
                                          Select coins Order By coins.WhatCoin.Denomination Descending


        Dim currentValueToBreak = valueOfMoneyToBreak

        'todo: check if I can change value first, then adjust _stateOfCoins if can be done
        'else leave _stateOfCoins as is, and return inserted money

        If listOfCoinsWithDenomination.ToList.Count > 0 Then

            For Each item In listOfCoinsWithDenomination
                Dim numberOfThisValueCoins = CInt(currentValueToBreak / item.WhatCoin.Denomination)
                If numberOfThisValueCoins <= item.Quantity Then
                    'give all
                    Dim myCoins As New PackOfCoins(item.WhatCoin, numberOfThisValueCoins)
                    returnList.Add(myCoins)
                    Dim _item = item
                    _stateOfCoins.Find(Function(c) _item.WhatCoin.Denomination = c.WhatCoin.Denomination).Quantity -= numberOfThisValueCoins
                    currentValueToBreak -= numberOfThisValueCoins * item.WhatCoin.Denomination
                    If currentValueToBreak = 0 Then
                        Exit For
                    End If
                Else
                    'give what is in, and continue with smaller coins
                    Dim whatIHave = item.Quantity * item.WhatCoin.Denomination
                    currentValueToBreak -= whatIHave
                    If item.Quantity > 0 Then
                        Dim myCoins As New PackOfCoins(item.WhatCoin, item.Quantity)
                        returnList.Add(myCoins)
                        Dim _item = item
                        _stateOfCoins.Find(Function(c) _item.WhatCoin.Denomination = c.WhatCoin.Denomination).Quantity -= item.Quantity

                    End If
                    If currentValueToBreak = 0 Then
                        Exit For
                    End If
                End If

            Next

        Else
            RaiseEvent NoMoreCoinsInMachine(Me, "No more coins in machine. Returning all your money.")
        End If


        Return returnList
    End Function

    Private Sub SortCoins(ByRef coinList As List(Of PackOfCoins))
        Dim sortedList As New List(Of PackOfCoins)
        Dim query As IEnumerable(Of PackOfCoins) = coinList.OrderByDescending(Function(c) c.WhatCoin.Denomination)
        sortedList.AddRange(query)
        coinList = sortedList
    End Sub
#End Region
End Class

Coin, PackOfCoin, Goods, PackOfGoods:

Spoiler

Public Class Coin
    Private _denomination As Decimal
    Public ReadOnly Property Denomination As Decimal
        Get
            Return _denomination
        End Get
    End Property
    Public Sub New(ByVal coinValue As Decimal)
        If coinValue < 0.01 Or coinValue > 1000 Then
            Throw New ArgumentException With {.Source = "Money value should be in range of 0.01 to 1000."}
            Exit Sub
        ElseIf coinValue >= 1 AndAlso CInt(coinValue) <> coinValue Then
            Throw New ArgumentException With {.Source = "Money with value greater than 1, should be integers."}
            Exit Sub
        End If
        _denomination = coinValue
    End Sub
End Class

Public Class PackOfCoins
    Public Property WhatCoin As Coin 'decimal, because we can have quarter of EUR or $
    Public Property Quantity As Integer

    Public Sub New(ByVal myCoin As Coin, ByVal NumberOfCoins As Integer)
        Me.WhatCoin = myCoin
        Me.Quantity = NumberOfCoins
    End Sub
End Class

Public Class Goods
    Public Property Name As String
    Public Property Price As Decimal

    Public Sub New(ByVal myPrice As Decimal, ByVal name As String)
        Me.Price = myPrice
        Me.Name = name
    End Sub
End Class

Public Class PackOfGoods
    Public Property WhatGoods As Goods
    Public Property Quantity As Integer

    Public Sub New(ByVal myGoods As Goods, ByVal NumberOfGoods As Integer)
        Me.WhatGoods = myGoods
        Me.Quantity = NumberOfGoods
    End Sub
End Class

Console testing:

Spoiler

Module Module1
    Private WithEvents myChangeMachine As ChangeMachine

    Sub Main()
        'initialize coins
        Dim myInitializedCoins As List(Of Coin) = InitializeCoins()

        'list of coins
        Dim myCoinList As List(Of PackOfCoins) = SetNumberOfEachCoinsForMachine(300, myInitializedCoins)

        'another list of coins
        Dim myInitializedCoins2 As List(Of Coin) = InitializeCoins()

        'another list of coin
        Dim myCoinList2 As List(Of PackOfCoins) = SetNumberOfEachCoinsForMachine(1500, myInitializedCoins2)
        Dim mewKindOfCoin As New Coin(10)
        Dim packOfNewKindOfCoin As New PackOfCoins(mewKindOfCoin, 50)
        myCoinList2.Add(packOfNewKindOfCoin)

        myChangeMachine = New ChangeMachine(myCoinList, "Machine 1", 1200, 50)
        myChangeMachine.RefillCoins(myCoinList2)

        'adding some goods
        Dim drink As New Goods(1.25, "Coca-Cola")
        Dim drink2 As New Goods(1.25, "Pepsi-Cola")

        Dim packOfDrink As New PackOfGoods(drink, 60)
        Dim packOfDrink2 As New PackOfGoods(drink2, 30)

        Dim listOfGoodsToAdd As New List(Of PackOfGoods)
        listOfGoodsToAdd.Add(packOfDrink)
        listOfGoodsToAdd.Add(packOfDrink2)

        myChangeMachine.AddGoods(listOfGoodsToAdd)

        Dim moneyToChange As New Coin(1000)
        Dim moneyToChange2 As New Coin(500)
        Dim packToChange2 As New PackOfCoins(moneyToChange, 5)
        Dim packToChange As New PackOfCoins(moneyToChange2, 8)
        Dim listOfMoneyToChange As New List(Of PackOfCoins) From {packToChange, packToChange2}

        myChangeMachine.ChangeCoins(listOfMoneyToChange)

        Console.ReadLine()
    End Sub

#Region "Private methods"

    Private Function InitializeCoins()
        Dim oneCent As New Coin(0.01)
        Dim twoCents As New Coin(0.02)
        Dim fiveCents As New Coin(0.05)
        Dim tenCents As New Coin(0.1)
        Dim twentyCents As New Coin(0.2)
        Dim fiftyCents As New Coin(0.5)
        Dim oneCoin As New Coin(1)
        Dim twoCoins As New Coin(2)

        Return New List(Of Coin) From {oneCent, twoCents, fiveCents, tenCents, twentyCents, fiftyCents, oneCoin, twoCoins}
    End Function

    Private Function SetNumberOfEachCoinsForMachine(ByVal numberOfCoins As Integer, myCoins As List(Of Coin)) As List(Of PackOfCoins)
        Dim returnMe As New List(Of PackOfCoins)
        For Each item In myCoins
            Dim addMeToList As New PackOfCoins(item, numberOfCoins)
            returnMe.Add(addMeToList)
        Next

        Return returnMe
    End Function

#End Region

#Region "Event handling methods"
    Private Sub CoinsFilled(ByRef sender As ChangeMachine, ByVal message As String, ByVal coinsReturned As List(Of PackOfCoins)) Handles myChangeMachine.CoinSupplyFiled
        Console.WriteLine("Machine {0} is saying: ""{1}""", sender.Name, message)
        For Each coins In coinsReturned
            Dim thisCoins = coins
            Console.WriteLine("Returned coins: {0} units of {1} valued coins. Machine {2} now holds {3} coins of this denomination.",
                              coins.Quantity, coins.WhatCoin.Denomination, sender.Name,
                              sender.StateOfCoins.Find(Function(c) c.WhatCoin.Denomination = thisCoins.WhatCoin.Denomination).Quantity)
        Next
    End Sub

    Private Sub GoodsFilled(ByRef sender As ChangeMachine, ByVal message As String, ByVal returnedGoods As List(Of PackOfGoods)) Handles myChangeMachine.GoodsAdded
        Console.WriteLine("Machine {0} is saying: ""{1}""", sender.Name, message)
        For Each retGoods In returnedGoods
            Dim thisGoods = retGoods
            Console.WriteLine("Returned goods: {0} units of {1}. Machine {2} now holds {3} units of {0}.",
                              retGoods.Quantity, retGoods.WhatGoods.Name, sender.Name,
                              sender.StateOfGoods.Find(Function(c) c.WhatGoods.Name = thisGoods.WhatGoods.Name).Quantity)
        Next

    End Sub

    Private Sub NoMoreCoins(ByRef sender As ChangeMachine, ByVal message As String) Handles myChangeMachine.NoMoreCoinsInMachine
        Console.WriteLine("Machine {0} is saying: ""{1}""", sender.Name, message)
    End Sub

    Private Sub CoinsChanged(ByRef sender As ChangeMachine, ByVal message As String, ByVal returnedCoins As List(Of List(Of PackOfCoins))) Handles myChangeMachine.CoinsChanged
        Console.WriteLine("Machine {0} is saying: ""{1}""", sender.Name, message)
        Dim sumOfCoins As Double
        For Each retCoins In returnedCoins
            For Each pack In retCoins
                Dim currentPackValue As Double = pack.Quantity * pack.WhatCoin.Denomination

                Dim _pack = pack
                Console.WriteLine("Returned coins: {0} units of {1}. Machine {2} now holds {3} coins of this denomination alltogeather. Current pack value: {4}",
                             pack.Quantity, pack.WhatCoin.Denomination, sender.Name,
                             sender.StateOfCoins.Find(Function(c) c.WhatCoin.Denomination = _pack.WhatCoin.Denomination).Quantity,
                             currentPackValue)

                sumOfCoins += _pack.Quantity * _pack.WhatCoin.Denomination
            Next
        Next
        Console.WriteLine("Sum of returned coins: {0}!", sumOfCoins)
    End Sub
#End Region
End Module

This post has been edited by lucky3: 03 October 2012 - 12:57 AM

[AdamSpeight2008]

The change machine shouldn't really know anything about the goods,that is the job of the Vending Machine. It only really needs to know the total price.

The change machine should only handle the job of coin insertion and the producing of any change.

[Keypad]-->[Vending Machine]---{Sale Price Changed}-->[ Change Machine ]
 {Goods}<--                 <--{Coin Inserted}--------                  ---{Change}-->
                            ---{Refund Coins}-------->
                            <--{Price Met}------------   

Note: You may have use the expanded view of the code.

Partial view of my submission.

Spoiler

  Private Sub HandleCoinInsertion(sender As Object, e As CoinInsertedEventArgs) Handles Me.CoinInserted
    If ThisCoinIsValid(e.Coin) Then
      ' Coin is valid. Add coin to collection slot '
      CoinsUserInserted.Add(e.Coin)
      Dim ValueOfCoinsUserInserted = CoinsUserInserted.Sum(Function(c) c.Value)
      Select Case _State
        Case ChangeMachineState.NotInUse
          RaiseEvent CoinReturned(Me, New CoinReturnedEventArgs(e.Coin))
        Case ChangeMachineState.ExactChangeOnly
          If ValueOfCoinsUserInserted > _SalePrice Then
            RaiseEvent CoinReturned(Me, New CoinReturnedEventArgs(e.Coin))
          ElseIf ValueOfCoinsUserInserted = _SalePrice Then
            RaiseEvent CoinsMeetSalePrice(Me, New CoinsMeetSalePriceEventArgs(CoinsUserInserted))
          End If
        Case ChangeMachineState.ChangeGiven
          If ValueOfCoinsUserInserted = _SalePrice Then RaiseEvent CoinsMeetSalePrice(Me, New CoinsMeetSalePriceEventArgs(CoinsUserInserted))
        Case ChangeMachineState.NoChangeGiven
          If ValueOfCoinsUserInserted = _SalePrice Then RaiseEvent CoinsMeetSalePrice(Me, New CoinsMeetSalePriceEventArgs(CoinsUserInserted))
        Case Else
          RaiseEvent CoinReturned(Me, New CoinReturnedEventArgs(e.Coin))
      End Select
    Else
      ' Coin is invalid so return it '
      RaiseEvent CoinReturned(Me, New CoinReturnedEventArgs(e.Coin))
    End If
  End Sub

  Public Sub InsertCoin(Coin As Coinage.Coin)
    SyncLock _Lock
      If _SalePrice.HasValue = False Then
        RaiseEvent CoinReturned(Me, New CoinReturnedEventArgs(Coin))
      Else
        RaiseEvent CoinInserted(Me, New CoinInsertedEventArgs(Coin))
      End If
    End SyncLock
  End Sub

This post has been edited by AdamSpeight2008: 03 October 2012 - 07:42 AM

[lucky3]

I have a strange problem with Double type variable, where I'm calculating sum of inserted/returned money. Although I'm inserting money with values in range 0.01 to 1000, I get sum of total with 500.25000000000001 and similar. Where the hell does those 000000000001 come from? Does this has something to do with threading and concurrency?

Here I have just some basic classes:

Spoiler

Testing in console:

Module Module1
    Private WithEvents myMoneyInsertPart As New MoneyInsertHardwarePart(AcceptingMoney.Accepting, 5000)

    Sub Main()
        Dim listOfMyCoins As New List(Of Money)
        Dim twoDollars As New Money(CoinsMoney.TwoCoin)
        Dim fiveCents As New Money(CentsMoney.FiveCent)
        Dim tenCents As New Money(CentsMoney.TenCent)
        Dim fiveBucks As New Money(CoinsMoney.FiveCoin)
        For n = 1 To 35
            listOfMyCoins.Add(twoDollars)
            listOfMyCoins.Add(fiveCents)
            listOfMyCoins.Add(tenCents)
            listOfMyCoins.Add(fiveBucks)
        Next

        For Each item In listOfMyCoins
            myMoneyInsertPart.InsertMoney(item)
        Next

        Threading.Thread.Sleep(4500)
        For Each item In listOfMyCoins
            myMoneyInsertPart.InsertMoney(item)
        Next
        Console.ReadLine()
    End Sub

#Region "Event handling methods"
    Private Sub myMoneyInsertPart_MoneyInserted(sender As Object, e As ConsoleApplication1.Money) Handles myMoneyInsertPart.MoneyInserted
        Console.WriteLine("{0} recieved {1}, of {2} value.", sender.name, e.CoinName, e.Denomination)
    End Sub

    Private Sub myMoneyInsertPart_MoneyRejected(sender As Object, e As ConsoleApplication1.MoneyInsertRejectedEventArgs) Handles myMoneyInsertPart.MoneyRejected
        Console.WriteLine("{0} is saying: ""{1}"", and has returned {2} money.", sender.name, e.RejectionMessage, e.RejectedMoney.CoinName)
    End Sub

    Private Sub myMoneyInsertPart_MoneyReturned(sender As Object, e As ConsoleApplication1.MoneyReturnedEventArgs) Handles myMoneyInsertPart.MoneyReturned
        Console.WriteLine("{0} is saying: ""{1}"", and has returned {2} pieces of money, valued {3} total.", sender.name, e.AcceptanceMessage, e.AcceptedMoney.Count, e.TotalValueOfAcceptedMoney)
    End Sub
#End Region
End Module

Money Class:

Public Class Money
#Region "Properties"
    Private _coinName As String
    Public ReadOnly Property CoinName As String
        Get
            Return _coinName
        End Get
    End Property

    Private _denomination As Double
    Public ReadOnly Property Denomination As Double
        Get
            Return _denomination
        End Get
    End Property
#End Region
    
#Region "Constructors"
    Private Sub New(ByVal name As String)
        _coinName = name
    End Sub

    Public Sub New(ByVal coinValue As CoinsMoney)
        Me.New(coinValue.ToString)
        _denomination = coinValue
    End Sub

    Public Sub New(ByVal coinValue As CentsMoney)
        Me.New(coinValue.ToString)
        _denomination = coinValue / 100
    End Sub

    Public Sub New(ByVal coinValue As PaperMoney)
        Me.New(coinValue.ToString)
        _denomination = coinValue
    End Sub
#End Region
End Class

Public Enum MoneyKind
    CentsMoney
    CoinsMoney
    PaperMoney
End Enum

Public Enum CentsMoney
    OneCent = 1
    TwoCent = 2
    FiveCent = 5
    TenCent = 10
    TwentyCent = 20
    FiftyCent = 50
End Enum

Public Enum CoinsMoney
    OneCoin = 1
    TwoCoin = 2
    FiveCoin = 5
End Enum

Public Enum PaperMoney
    TenPaper = 10
    TwentyPaper = 20
    FiftyPaper = 50
    HundredPaper = 100
    TwoHundredPaper = 200
    FiveHundredPaper = 500
    TousandPaper = 1000
End Enum

MoneyInsertPart Class:

Imports System.Collections.ObjectModel
Imports System.Collections.Concurrent


Public Class MoneyInsertHardwarePart
#Region "Constructors"
    Public Sub New()
        Me.New(AcceptingMoney.Accepting)
    End Sub

    Public Sub New(ByVal doesItAcceptMoney As AcceptingMoney)
        Me.New(doesItAcceptMoney, 180000)
    End Sub

    Public Sub New(ByVal name As String)
        Me.New(AcceptingMoney.Accepting)
        _name = name
    End Sub

    Public Sub New(ByVal doesItAcceptMoney As AcceptingMoney, ByVal timeOfInactivityToReturnMoney As Integer)
        DoesAcceptMoney = doesItAcceptMoney
        inactivityForTimer = timeOfInactivityToReturnMoney
        myMoney = New ObservableCollection(Of Money)
        If _name = "" Then
            _name = "Money Insert HW Part"
        End If
    End Sub
#End Region

#Region "Properties"
    Public Property DoesAcceptMoney As AcceptingMoney
    Private WithEvents myMoney As ObservableCollection(Of Money)
    Private Property inactivityForTimer As Integer
    Private Property _sumOfInsertedMoney As Double
    Public ReadOnly Property SumOfInsertedMoney As Double
        Get
            Return Math.Round(_sumOfInsertedMoney, 3)
        End Get
    End Property


    Private Property _name As String
    Public ReadOnly Property Name As String
        Get
            Return _name
        End Get
    End Property

    Private WithEvents myNoActivityTimer As System.Timers.Timer
#End Region

#Region "Events"
    Public Event MoneyAccepted(ByVal sender As Object, ByVal e As MoneyInsertAcceptedEventArgs)
    Public Event MoneyRejected(ByVal sender As Object, ByVal e As MoneyInsertRejectedEventArgs)
    Public Event MoneyInserted(ByVal sender As Object, ByVal e As Money)
    Public Event MoneyReturned(ByVal sender As Object, ByVal e As MoneyReturnedEventArgs)
#End Region

#Region "Public Methods"
    Public Sub InsertMoney(ByVal money As Money)
        If DoesAcceptMoney = AcceptingMoney.NotAccepting Then
            RaiseEvent MoneyRejected(Me, New MoneyInsertRejectedEventArgs(money, "Sorry. Machine currently not accepting money."))
        Else
            AddToBalance(money)
            RaiseEvent MoneyInserted(Me, money)
        End If
    End Sub

    Public Function PassTheMoney(ByVal money As List(Of Money), ByVal returnTheRest As Boolean) As List(Of Money)
        Dim returnList As New List(Of Money)
        For Each item In money
            If myMoney.Contains(item) Then
                returnList.Add(item)
                SubstractFromBalance(item)
            End If
        Next

        RaiseEvent MoneyAccepted(Me, New MoneyInsertAcceptedEventArgs(returnList, "Money accepted!"))

        If returnTheRest Then
            ReturnTheRemainingMoney()
        End If
        Return returnList
    End Function

    Public Sub ReturnTheRemainingMoney(Optional message As String = "Returning the remaining money.")
        Dim returnList As New List(Of Money)
        For n = 0 To myMoney.Count - 1
            returnList.Add(myMoney(n))
        Next
        SubstractFromBalance(returnList)

        RaiseEvent MoneyReturned(Me, New MoneyReturnedEventArgs(returnList, message))
    End Sub
#End Region

#Region "Private Methods"
    Private Sub AddToBalance(ByVal money As Money)
        myMoney.Add(money)
        _sumOfInsertedMoney += Math.Round(money.Denomination, 3)
    End Sub

    Private Sub AddToBalance(ByVal moneyList As List(Of Money))
        For n = 0 To moneyList.Count - 1
            myMoney.Add(moneyList(n))
            _sumOfInsertedMoney += Math.Round(moneyList(n).Denomination, 3)
        Next
    End Sub

    Private Sub SubstractFromBalance(ByVal money As Money)
        _sumOfInsertedMoney -= Math.Round(money.Denomination, 3)
        myMoney.Remove(money)
    End Sub

    Private Sub SubstractFromBalance(ByVal moneyList As List(Of Money))
        For n = 0 To moneyList.Count - 1
            _sumOfInsertedMoney -= Math.Round(moneyList(n).Denomination, 3)
            myMoney.Remove(moneyList(n))
        Next
    End Sub
#End Region

#Region "Events handling"
    Private Sub StartTimer() Handles Me.MoneyInserted
        If IsNothing(myNoActivityTimer) Then
            myNoActivityTimer = New System.Timers.Timer With {.Interval = inactivityForTimer, .Enabled = True}
            myNoActivityTimer.Start()
        Else
            myNoActivityTimer.Stop()
            myNoActivityTimer.Start()
        End If
    End Sub

    Private Sub TimeElapsed() Handles myNoActivityTimer.Elapsed
        ReturnTheRemainingMoney("No activity for set time period. Returning all the remaining money.")
    End Sub

    Private Sub myMoney_Collectionchanged(sender As Object, e As System.Collections.Specialized.NotifyCollectionchangedEventArgs) Handles myMoney.Collectionchanged
        If FormatNumber(_sumOfInsertedMoney, 2) = 0 AndAlso IsNothing(myNoActivityTimer) = False Then
            myNoActivityTimer.Stop()
        End If
    End Sub
#End Region


End Class

Public Enum AcceptingMoney
    Accepting = True
    NotAccepting = False
End Enum

Event e classes:

Public Class MoneyInsertAcceptedEventArgs
#Region "Constructor"
    Public Sub New(ByVal money As List(Of Money), message As String)
        _acceptedMoney = money
        _acceptedMessage = message
    End Sub
#End Region

#Region "Properties"
    Private Property _acceptedMoney As List(Of Money)
    Public ReadOnly Property AcceptedMoney As List(Of Money)
        Get
            Return _acceptedMoney
        End Get
    End Property

    Private Property _acceptedMessage As String
    Public ReadOnly Property AcceptanceMessage As String
        Get
            Return _acceptedMessage
        End Get
    End Property

    Private Property _totalValue As Double
    Public ReadOnly Property TotalValueOfAcceptedMoney As Double
        Get
            CalculateTotal()
            Return _totalValue
        End Get
    End Property
#End Region
    
#Region "Methods"
    Private Sub CalculateTotal()
        _totalValue = 0
        For Each item In AcceptedMoney
            _totalValue += item.Denomination
        Next
    End Sub
#End Region
End Class

Public Class MoneyReturnedEventArgs
    Inherits MoneyInsertAcceptedEventArgs

    Public Sub New(ByVal money As List(Of Money), message As String)
        MyBase.new(money, message)
    End Sub
End Class

Public Class MoneyInsertRejectedEventArgs
    Public Sub New(ByVal money As Money, message As String)
        _rejectedMoney = money
        _rejectionMessage = message
    End Sub

    Private Property _rejectedMoney As Money
    Public ReadOnly Property RejectedMoney As Money
        Get
            Return _rejectedMoney
        End Get
    End Property

    Private Property _rejectionMessage As String
    Public ReadOnly Property RejectionMessage As String
        Get
            Return _rejectionMessage
        End Get
    End Property
End Class

[lar3ry]

lucky3, on 04 October 2012 - 08:39 AM, said:

I have a strange problem with Double type variable...
I get sum of total with 500.25000000000001 and similar. Where the hell does those 000000000001 come from? Does this has something to do with threading and concurrency?

Probably comes from the normal behaviour of a double. Basically just rounding errors. Comparing two doubles is almost always problematic for that reason, and you are better off rounding to the number of decimal points, or using the decimal data type.

[LilGhost]

lucky3, on 04 October 2012 - 08:39 AM, said:

I have a strange problem with Double type variable, where I'm calculating sum of inserted/returned money. Although I'm inserting money with values in range 0.01 to 1000, I get sum of total with 500.25000000000001 and similar. Where the hell does those 000000000001 come from? Does this has something to do with threading and concurrency?

Here I have just some basic classes:

Spoiler

Testing in console:

Module Module1
    Private WithEvents myMoneyInsertPart As New MoneyInsertHardwarePart(AcceptingMoney.Accepting, 5000)

    Sub Main()
        Dim listOfMyCoins As New List(Of Money)
        Dim twoDollars As New Money(CoinsMoney.TwoCoin)
        Dim fiveCents As New Money(CentsMoney.FiveCent)
        Dim tenCents As New Money(CentsMoney.TenCent)
        Dim fiveBucks As New Money(CoinsMoney.FiveCoin)
        For n = 1 To 35
            listOfMyCoins.Add(twoDollars)
            listOfMyCoins.Add(fiveCents)
            listOfMyCoins.Add(tenCents)
            listOfMyCoins.Add(fiveBucks)
        Next

        For Each item In listOfMyCoins
            myMoneyInsertPart.InsertMoney(item)
        Next

        Threading.Thread.Sleep(4500)
        For Each item In listOfMyCoins
            myMoneyInsertPart.InsertMoney(item)
        Next
        Console.ReadLine()
    End Sub

#Region "Event handling methods"
    Private Sub myMoneyInsertPart_MoneyInserted(sender As Object, e As ConsoleApplication1.Money) Handles myMoneyInsertPart.MoneyInserted
        Console.WriteLine("{0} recieved {1}, of {2} value.", sender.name, e.CoinName, e.Denomination)
    End Sub

    Private Sub myMoneyInsertPart_MoneyRejected(sender As Object, e As ConsoleApplication1.MoneyInsertRejectedEventArgs) Handles myMoneyInsertPart.MoneyRejected
        Console.WriteLine("{0} is saying: ""{1}"", and has returned {2} money.", sender.name, e.RejectionMessage, e.RejectedMoney.CoinName)
    End Sub

    Private Sub myMoneyInsertPart_MoneyReturned(sender As Object, e As ConsoleApplication1.MoneyReturnedEventArgs) Handles myMoneyInsertPart.MoneyReturned
        Console.WriteLine("{0} is saying: ""{1}"", and has returned {2} pieces of money, valued {3} total.", sender.name, e.AcceptanceMessage, e.AcceptedMoney.Count, e.TotalValueOfAcceptedMoney)
    End Sub
#End Region
End Module

Money Class:

Public Class Money
#Region "Properties"
    Private _coinName As String
    Public ReadOnly Property CoinName As String
        Get
            Return _coinName
        End Get
    End Property

    Private _denomination As Double
    Public ReadOnly Property Denomination As Double
        Get
            Return _denomination
        End Get
    End Property
#End Region
    
#Region "Constructors"
    Private Sub New(ByVal name As String)
        _coinName = name
    End Sub

    Public Sub New(ByVal coinValue As CoinsMoney)
        Me.New(coinValue.ToString)
        _denomination = coinValue
    End Sub

    Public Sub New(ByVal coinValue As CentsMoney)
        Me.New(coinValue.ToString)
        _denomination = coinValue / 100
    End Sub

    Public Sub New(ByVal coinValue As PaperMoney)
        Me.New(coinValue.ToString)
        _denomination = coinValue
    End Sub
#End Region
End Class

Public Enum MoneyKind
    CentsMoney
    CoinsMoney
    PaperMoney
End Enum

Public Enum CentsMoney
    OneCent = 1
    TwoCent = 2
    FiveCent = 5
    TenCent = 10
    TwentyCent = 20
    FiftyCent = 50
End Enum

Public Enum CoinsMoney
    OneCoin = 1
    TwoCoin = 2
    FiveCoin = 5
End Enum

Public Enum PaperMoney
    TenPaper = 10
    TwentyPaper = 20
    FiftyPaper = 50
    HundredPaper = 100
    TwoHundredPaper = 200
    FiveHundredPaper = 500
    TousandPaper = 1000
End Enum

MoneyInsertPart Class:

Imports System.Collections.ObjectModel
Imports System.Collections.Concurrent


Public Class MoneyInsertHardwarePart
#Region "Constructors"
    Public Sub New()
        Me.New(AcceptingMoney.Accepting)
    End Sub

    Public Sub New(ByVal doesItAcceptMoney As AcceptingMoney)
        Me.New(doesItAcceptMoney, 180000)
    End Sub

    Public Sub New(ByVal name As String)
        Me.New(AcceptingMoney.Accepting)
        _name = name
    End Sub

    Public Sub New(ByVal doesItAcceptMoney As AcceptingMoney, ByVal timeOfInactivityToReturnMoney As Integer)
        DoesAcceptMoney = doesItAcceptMoney
        inactivityForTimer = timeOfInactivityToReturnMoney
        myMoney = New ObservableCollection(Of Money)
        If _name = "" Then
            _name = "Money Insert HW Part"
        End If
    End Sub
#End Region

#Region "Properties"
    Public Property DoesAcceptMoney As AcceptingMoney
    Private WithEvents myMoney As ObservableCollection(Of Money)
    Private Property inactivityForTimer As Integer
    Private Property _sumOfInsertedMoney As Double
    Public ReadOnly Property SumOfInsertedMoney As Double
        Get
            Return Math.Round(_sumOfInsertedMoney, 3)
        End Get
    End Property


    Private Property _name As String
    Public ReadOnly Property Name As String
        Get
            Return _name
        End Get
    End Property

    Private WithEvents myNoActivityTimer As System.Timers.Timer
#End Region

#Region "Events"
    Public Event MoneyAccepted(ByVal sender As Object, ByVal e As MoneyInsertAcceptedEventArgs)
    Public Event MoneyRejected(ByVal sender As Object, ByVal e As MoneyInsertRejectedEventArgs)
    Public Event MoneyInserted(ByVal sender As Object, ByVal e As Money)
    Public Event MoneyReturned(ByVal sender As Object, ByVal e As MoneyReturnedEventArgs)
#End Region

#Region "Public Methods"
    Public Sub InsertMoney(ByVal money As Money)
        If DoesAcceptMoney = AcceptingMoney.NotAccepting Then
            RaiseEvent MoneyRejected(Me, New MoneyInsertRejectedEventArgs(money, "Sorry. Machine currently not accepting money."))
        Else
            AddToBalance(money)
            RaiseEvent MoneyInserted(Me, money)
        End If
    End Sub

    Public Function PassTheMoney(ByVal money As List(Of Money), ByVal returnTheRest As Boolean) As List(Of Money)
        Dim returnList As New List(Of Money)
        For Each item In money
            If myMoney.Contains(item) Then
                returnList.Add(item)
                SubstractFromBalance(item)
            End If
        Next

        RaiseEvent MoneyAccepted(Me, New MoneyInsertAcceptedEventArgs(returnList, "Money accepted!"))

        If returnTheRest Then
            ReturnTheRemainingMoney()
        End If
        Return returnList
    End Function

    Public Sub ReturnTheRemainingMoney(Optional message As String = "Returning the remaining money.")
        Dim returnList As New List(Of Money)
        For n = 0 To myMoney.Count - 1
            returnList.Add(myMoney(n))
        Next
        SubstractFromBalance(returnList)

        RaiseEvent MoneyReturned(Me, New MoneyReturnedEventArgs(returnList, message))
    End Sub
#End Region

#Region "Private Methods"
    Private Sub AddToBalance(ByVal money As Money)
        myMoney.Add(money)
        _sumOfInsertedMoney += Math.Round(money.Denomination, 3)
    End Sub

    Private Sub AddToBalance(ByVal moneyList As List(Of Money))
        For n = 0 To moneyList.Count - 1
            myMoney.Add(moneyList(n))
            _sumOfInsertedMoney += Math.Round(moneyList(n).Denomination, 3)
        Next
    End Sub

    Private Sub SubstractFromBalance(ByVal money As Money)
        _sumOfInsertedMoney -= Math.Round(money.Denomination, 3)
        myMoney.Remove(money)
    End Sub

    Private Sub SubstractFromBalance(ByVal moneyList As List(Of Money))
        For n = 0 To moneyList.Count - 1
            _sumOfInsertedMoney -= Math.Round(moneyList(n).Denomination, 3)
            myMoney.Remove(moneyList(n))
        Next
    End Sub
#End Region

#Region "Events handling"
    Private Sub StartTimer() Handles Me.MoneyInserted
        If IsNothing(myNoActivityTimer) Then
            myNoActivityTimer = New System.Timers.Timer With {.Interval = inactivityForTimer, .Enabled = True}
            myNoActivityTimer.Start()
        Else
            myNoActivityTimer.Stop()
            myNoActivityTimer.Start()
        End If
    End Sub

    Private Sub TimeElapsed() Handles myNoActivityTimer.Elapsed
        ReturnTheRemainingMoney("No activity for set time period. Returning all the remaining money.")
    End Sub

    Private Sub myMoney_Collectionchanged(sender As Object, e As System.Collections.Specialized.NotifyCollectionchangedEventArgs) Handles myMoney.Collectionchanged
        If FormatNumber(_sumOfInsertedMoney, 2) = 0 AndAlso IsNothing(myNoActivityTimer) = False Then
            myNoActivityTimer.Stop()
        End If
    End Sub
#End Region


End Class

Public Enum AcceptingMoney
    Accepting = True
    NotAccepting = False
End Enum

Event e classes:

Public Class MoneyInsertAcceptedEventArgs
#Region "Constructor"
    Public Sub New(ByVal money As List(Of Money), message As String)
        _acceptedMoney = money
        _acceptedMessage = message
    End Sub
#End Region

#Region "Properties"
    Private Property _acceptedMoney As List(Of Money)
    Public ReadOnly Property AcceptedMoney As List(Of Money)
        Get
            Return _acceptedMoney
        End Get
    End Property

    Private Property _acceptedMessage As String
    Public ReadOnly Property AcceptanceMessage As String
        Get
            Return _acceptedMessage
        End Get
    End Property

    Private Property _totalValue As Double
    Public ReadOnly Property TotalValueOfAcceptedMoney As Double
        Get
            CalculateTotal()
            Return _totalValue
        End Get
    End Property
#End Region
    
#Region "Methods"
    Private Sub CalculateTotal()
        _totalValue = 0
        For Each item In AcceptedMoney
            _totalValue += item.Denomination
        Next
    End Sub
#End Region
End Class

Public Class MoneyReturnedEventArgs
    Inherits MoneyInsertAcceptedEventArgs

    Public Sub New(ByVal money As List(Of Money), message As String)
        MyBase.new(money, message)
    End Sub
End Class

Public Class MoneyInsertRejectedEventArgs
    Public Sub New(ByVal money As Money, message As String)
        _rejectedMoney = money
        _rejectionMessage = message
    End Sub

    Private Property _rejectedMoney As Money
    Public ReadOnly Property RejectedMoney As Money
        Get
            Return _rejectedMoney
        End Get
    End Property

    Private Property _rejectionMessage As String
    Public ReadOnly Property RejectionMessage As String
        Get
            Return _rejectionMessage
        End Get
    End Property
End Class

Set your precision to 2.
That should fix any issues.