VB.NET Random类代码示例

Module Example
   Public Sub Main()
      ' Instantiate random number generator using system-supplied value as seed.
      Dim rand As New Random()
      ' Generate and display 5 random byte (integer) values.
      Dim bytes(4) As Byte
      rand.NextBytes(bytes)
      Console.WriteLine("Five random byte values:")
      For Each byteValue As Byte In bytes
         Console.Write("{0, 5}", byteValue)
      Next
      Console.WriteLine()   
      ' Generate and display 5 random integers.
      Console.WriteLine("Five random integer values:")
      For ctr As Integer = 0 To 4
         Console.Write("{0,15:N0}", rand.Next)
      Next                     
      Console.WriteLine()
      ' Generate and display 5 random integers between 0 and 100.'
      Console.WriteLine("Five random integers between 0 and 100:")
      For ctr As Integer = 0 To 4
         Console.Write("{0,8:N0}", rand.Next(101))
      Next                     
      Console.WriteLine()
      ' Generate and display 5 random integers from 50 to 100.
      Console.WriteLine("Five random integers between 50 and 100:")
      For ctr As Integer = 0 To 4
         Console.Write("{0,8:N0}", rand.Next(50, 101))
      Next                     
      Console.WriteLine()
      ' Generate and display 5 random floating point values from 0 to 1.
      Console.WriteLine("Five Doubles.")
      For ctr As Integer = 0 To 4
         Console.Write("{0,8:N3}", rand.NextDouble())
      Next                     
      Console.WriteLine()
      ' Generate and display 5 random floating point values from 0 to 5.
      Console.WriteLine("Five Doubles between 0 and 5.")
      For ctr As Integer = 0 To 4
         Console.Write("{0,8:N3}", rand.NextDouble() * 5)
      Next                     
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim rnd As New Random()
      Dim malePetNames() As String = { "Rufus", "Bear", "Dakota", "Fido", 
                                    "Vanya", "Samuel", "Koani", "Volodya", 
                                    "Prince", "Yiska" }
      Dim femalePetNames() As String = { "Maggie", "Penny", "Saya", "Princess", 
                                         "Abby", "Laila", "Sadie", "Olivia", 
                                         "Starlight", "Talla" }                                      
      
      ' Generate random indexes for pet names.
      Dim mIndex As Integer = rnd.Next(malePetNames.Length)
      Dim fIndex As Integer = rnd.Next(femalePetNames.Length)
      
      ' Display the result.
      Console.WriteLine("Suggested pet name of the day: ")
      Console.WriteLine("   For a male:     {0}", malePetNames(mIndex))
      Console.WriteLine("   For a female:   {0}", femalePetNames(fIndex))
   End Sub
End Module

Module modMain

   Public Sub Main()
      Dim bytes1(99), bytes2(99) As Byte
      Dim rnd1 As New Random()
      Dim rnd2 As New Random()
      
      rnd1.NextBytes(bytes1)
      rnd2.NextBytes(bytes2)
      
      Console.WriteLine("First Series:")
      For ctr As Integer = bytes1.GetLowerBound(0) to bytes1.GetUpperBound(0)
         Console.Write("{0, 5}", bytes1(ctr))
         If (ctr + 1) Mod 10 = 0 Then Console.WriteLine()
      Next 
      Console.WriteLine()
      Console.WriteLine("Second Series:")        
      For ctr As Integer = bytes2.GetLowerBound(0) to bytes2.GetUpperBound(0)
         Console.Write("{0, 5}", bytes2(ctr))
         If (ctr + 1) Mod 10 = 0 Then Console.WriteLine()
      Next   
   End Sub
End Module

' 导入命名空间
Imports System.Threading

Module Example
   <ThreadStatic> Dim previous As Double = 0.0
   <ThreadStatic> Dim perThreadCtr As Integer = 0
   <ThreadStatic> Dim perThreadTotal As Double = 0.0  
   Dim source As New CancellationTokenSource()
   Dim countdown As New CountdownEvent(1) 
   Dim randLock As New Object()
   Dim numericLock As New Object()
   Dim rand As New Random()
   Dim totalValue As Double = 0.0
   Dim totalCount As Integer = 0
   
   Public Sub Main()
      Thread.CurrentThread.Name = "Main"

      Dim token As CancellationToken = source.Token 
      For threads As Integer = 1 To 10
         Dim newThread As New Thread(AddressOf GetRandomNumbers)
         newThread.Name = threads.ToString()
         newThread.Start(token)
      Next
      GetRandomNumbers(token)
      
      countdown.Signal()
      ' Make sure all threads have finished.
      countdown.Wait()

      Console.WriteLine()
      Console.WriteLine("Total random numbers generated: {0:N0}", totalCount)
      Console.WriteLine("Total sum of all random numbers: {0:N2}", totalValue)
      Console.WriteLine("Random number mean: {0:N4}", totalValue/totalCount)
   End Sub

   Private Sub GetRandomNumbers(o As Object)
      Dim token As CancellationToken = CType(o, CancellationToken)
      Dim result As Double = 0.0
      countdown.AddCount(1)
         
      Try  
         For ctr As Integer = 1 To 2000000
            ' Make sure there's no corruption of Random.
            token.ThrowIfCancellationRequested()

            SyncLock randLock
               result = rand.NextDouble()
            End SyncLock
            ' Check for corruption of Random instance.
            If result = previous AndAlso result = 0 Then 
               source.Cancel()
            Else 
               previous = result
            End If
            perThreadCtr += 1
            perThreadTotal += result
         Next      
       
         Console.WriteLine("Thread {0} finished execution.", 
                           Thread.CurrentThread.Name)
         Console.WriteLine("Random numbers generated: {0:N0}", perThreadCtr)
         Console.WriteLine("Sum of random numbers: {0:N2}", perThreadTotal)
         Console.WriteLine("Random number mean: {0:N4}", perThreadTotal/perThreadCtr)
         Console.WriteLine()
         
         ' Update overall totals.
         SyncLock numericLock
            totalCount += perThreadCtr
            totalValue += perThreadTotal  
         End SyncLock
      Catch e As OperationCanceledException
         Console.WriteLine("Corruption in Thread {1}", e.GetType().Name, Thread.CurrentThread.Name)
      Finally 
         countdown.Signal()
         source.Dispose()
      End Try
   End Sub
End Module

' 导入命名空间
Imports System.Collections.Generic
Imports System.Threading
Imports System.Threading.Tasks

Module Example
   Dim source As New CancellationTokenSource()
   Dim randLock As New Object()
   Dim numericLock As New Object()
   Dim rand As New Random()
   Dim totalValue As Double = 0.0
   Dim totalCount As Integer = 0
   
   Public Sub Main()
      Dim tasks As New List(Of Task)()
      
      For ctr As Integer = 1 To 10
         Dim token As CancellationToken = source.Token 
         Dim taskNo As Integer = ctr
         tasks.Add(Task.Run( 
                   Sub()
                      Dim previous As Double = 0.0
                      Dim taskCtr As Integer = 0
                      Dim taskTotal As Double = 0.0
                      Dim result As Double = 0.0

                      For n As Integer = 1 To 2000000
                         ' Make sure there's no corruption of Random.
                         token.ThrowIfCancellationRequested()
      
                         SyncLock randLock
                           result = rand.NextDouble()
                         End SyncLock
                         ' Check for corruption of Random instance.
                         If result = previous AndAlso result = 0 Then
                           source.Cancel()
                         Else 
                           previous = result
                         End If
                        taskCtr += 1
                        taskTotal += result
                      Next   

                      ' Show result.
                     Console.WriteLine("Task {0} finished execution.", taskNo)
                     Console.WriteLine("Random numbers generated: {0:N0}", taskCtr)
                     Console.WriteLine("Sum of random numbers: {0:N2}", taskTotal)
                     Console.WriteLine("Random number mean: {0:N4}", taskTotal/taskCtr)
                     Console.WriteLine()
                     
                     ' Update overall totals.
                     SyncLock numericLock
                        totalCount += taskCtr
                        totalValue += taskTotal  
                     End SyncLock
                   End Sub, token))
      Next

      Try
         Task.WaitAll(tasks.ToArray())
         Console.WriteLine()
         Console.WriteLine("Total random numbers generated: {0:N0}", totalCount)
         Console.WriteLine("Total sum of all random numbers: {0:N2}", totalValue)
         Console.WriteLine("Random number mean: {0:N4}", totalValue/totalCount)
      Catch e As AggregateException
         For Each inner As Exception In e.InnerExceptions
            Dim canc As TaskCanceledException = TryCast(inner, TaskCanceledException)
            If canc IsNot Nothing Then
               Console.WriteLine("Task #{0} cancelled.", canc.Task.Id)
            Else
               Console.WriteLine("Exception: {0}", inner.GetType().Name)
            End If   
         Next         
      Finally
         source.Dispose()
      End Try
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim rnd As New Random()
      Dim bytes(19) As Byte
      rnd.NextBytes(bytes)  
      For ctr As Integer = 1 To bytes.Length
         Console.Write("{0,3}   ", bytes(ctr - 1))
         If ctr Mod 10 = 0 Then Console.WriteLine()
      Next 
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim rnd As New Random()
      For ctr As Integer = 0 To 9
         Console.Write("{0,3}   ", rnd.Next(-10, 11))
      Next
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim rnd As New Random()
      For ctr As Integer = 0 To 9
         Console.Write("{0,-19:R}   ", rnd.NextDouble())
         If (ctr + 1) Mod 3 = 0 Then Console.WriteLine()
      Next
   End Sub
End Module

' 导入命名空间
Imports System.Threading

Module Example
   Public Sub Main()
      Console.WriteLine("Instantiating two random number generators...")
      Dim rnd1 As New Random()
      Thread.Sleep(2000)
      Dim rnd2 As New Random()
      Console.WriteLine()
      
      Console.WriteLine("The first random number generator:")
      For ctr As Integer = 1 To 10
         Console.WriteLine("   {0}", rnd1.Next())
      Next  
      Console.WriteLine()
       
      Console.WriteLine("The second random number generator:")
      For ctr As Integer = 1 To 10
         Console.WriteLine("   {0}", rnd2.Next())
      Next   
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim rnd As New Random()
      For ctr As Integer = 1 To 15
         Console.Write("{0,3}    ", rnd.Next(-10, 11))
         If ctr Mod 5 = 0 Then Console.WriteLine()
      Next   
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim rnd As New Random()
      For ctr As Integer = 1 To 50
         Console.Write("{0,3}    ", rnd.Next(1000, 10000))
         If ctr Mod 10 = 0 Then Console.WriteLine()
      Next   
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim rnd As New Random()
      For ctr As Integer = 1 To 10
         Console.WriteLine(rnd.NextDouble() - 1)
      Next
   End Sub
End Module

Module Example
   Public Sub Main()
      Const ONE_TENTH As Long = 922337203685477581

      Dim rnd As New Random()
      Dim number As Long
      Dim count(9) As Integer
      
      ' Generate 20 million integer values.
      For ctr As Integer = 1 To 20000000
         number = CLng(rnd.NextDouble() * Int64.MaxValue)
         ' Categorize random numbers.
         count(CInt(number \ ONE_TENTH)) += 1
      Next
      ' Display breakdown by range.
      Console.WriteLine("{0,28} {1,32}   {2,7}", "Range", "Count", "Pct.")
      Console.WriteLine()
      For ctr As Integer = 0 To 9
         Console.WriteLine("{0,25:N0}-{1,25:N0}  {2,8:N0}   {3,7:P2}", ctr * ONE_TENTH,
                            If(ctr < 9, ctr * ONE_TENTH + ONE_TENTH - 1, Int64.MaxValue), 
                            count(ctr), count(ctr)/20000000)
      Next
   End Sub
End Module

Module Example
   Public Sub Main()
      Dim rnd As New Random()
      Dim lowerBound As Integer = 10
      Dim upperBound As Integer = 11
      Dim range(9) As Integer
      For ctr As Integer = 1 To 1000000
         Dim value As Double = rnd.NextDouble() * (upperBound - lowerBound) + lowerBound
         range(CInt(Math.Truncate((value - lowerBound) * 10))) += 1 
      Next
      
      For ctr As Integer = 0 To 9
         Dim lowerRange As Double = 10 + ctr * .1
         Console.WriteLine("{0:N1} to {1:N1}: {2,8:N0}  ({3,7:P2})", 
                           lowerRange, lowerRange + .1, range(ctr), 
                           range(ctr) / 1000000.0)
      Next 
   End Sub
End Module

Module Example
   Public Sub Main()
      ' Instantiate the Boolean generator.
      Dim boolGen As New BooleanGenerator()
      Dim totalTrue, totalFalse As Integer 
      
      ' Generate 1,0000 random Booleans, and keep a running total.
      For ctr As Integer = 0 To 9999999
          Dim value As Boolean = boolGen.NextBoolean()
          If value Then
             totalTrue += 1
          Else
             totalFalse += 1
          End If
      Next
      Console.WriteLine("Number of true values:  {0,7:N0} ({1:P3})", 
                        totalTrue, 
                        totalTrue/(totalTrue + totalFalse))
      Console.WriteLine("Number of false values: {0,7:N0} ({1:P3})", 
                        totalFalse, 
                        totalFalse/(totalTrue + totalFalse))
   End Sub                     
End Module

Public Class BooleanGenerator
   Dim rnd As Random
   
   Public Sub New()
      rnd = New Random()
   End Sub

   Public Function NextBoolean() As Boolean
      Return Convert.ToBoolean(rnd.Next(0, 2))
   End Function
End Class