Imports System.Threading

Module MultiThreading

    Public Buffer As Integer
    Public BufferEmpty As Boolean = True
    Public MonitorLock As Object = New Object()

    Sub Producer()
        Dim Value As Integer = 0
        Do
            Monitor.Enter(MonitorLock)
            If (BufferEmpty) Then
                BufferEmpty = False
                Buffer = Value

                If (Value = 0) Then
                    Value = 1
                Else
                    Value = 0
                End If

                Console.WriteLine("Parent: " & Buffer)

            End If
            Monitor.Exit(MonitorLock)

        Loop While (True)

    End Sub

    Sub Consumer()

        Dim Value As Integer

        Do
            Monitor.Enter(MonitorLock)

            If (Not BufferEmpty) Then
                BufferEmpty = True
                Thread.CurrentThread.Sleep(1000)

                Value = Buffer

                Console.WriteLine("Child: " & Value)

            End If

            Monitor.Exit(MonitorLock)

        Loop While (True)

    End Sub

    Sub Main()
        Dim ProducerThread As Thread
        Dim ConsumerThread As Thread

        ProducerThread = New Thread(AddressOf Producer)
        ConsumerThread = New Thread(AddressOf Consumer)

        ProducerThread.Start()
        ConsumerThread.Start()
    End Sub

End Module