Public Class pros_stack
Dim stk As New Stack(Of barang)

Private Sub beli(ByVal brg As barang)
    stk.Push(brg)
    stock += brg.jml
End Sub

Private Function jual() As barang
    Dim hps As barang = stk.Pop
    stock -= hps.jml
    Return hps
End Function

Public Sub proses()
    Dim putar As Boolean = True
    Dim pilih As Integer
    Dim new_brg As barang
    '
    Console.Clear()
    history.Clear()
    '
    Try
        Console.WriteLine("               Proses STACK")
        Console.WriteLine("               ------------")
        While putar
            Console.WriteLine("               Menu")
            Console.WriteLine("               1. Beli")
            Console.WriteLine("               2. Jual")
            Console.WriteLine("               3. Selesai")
            Console.WriteLine()
            Console.Write("Pilih : ")
            pilih = Console.ReadLine
            If pilih = 1 Then ' BELI
                Console.WriteLine("               Proses Beli")
                Console.WriteLine("               ----------")
                Console.Write("Jumlah Barang : ")
                new_brg.jml = Console.ReadLine
                Console.Write("Harga Satuan : ")
                new_brg.hrg = Console.ReadLine