# Random Classe

## Definição

Representa um gerador de número pseudoaleatório, que é um algoritmo que produz uma sequência de números que atendem a certos requisitos estatísticos de aleatoriedade.Represents a pseudo-random number generator, which is an algorithm that produces a sequence of numbers that meet certain statistical requirements for randomness.

public ref class Random
public class Random
[System.Serializable]
public class Random
[System.Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
public class Random
type Random = class
[<System.Serializable>]
type Random = class
[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type Random = class
Public Class Random
Herança
Random
Atributos

## Exemplos

O exemplo a seguir cria um gerador de número aleatório único e chama seus NextBytes Next métodos, e NextDouble para gerar sequências de números aleatórios em intervalos diferentes.The following example creates a single random number generator and calls its NextBytes, Next, and NextDouble methods to generate sequences of random numbers within different ranges.

using namespace System;

void main()
{
// Instantiate random number generator using system-supplied value as seed.
Random^ rand = gcnew Random();
// Generate and display 5 random byte (integer) values.
array<Byte>^ bytes = gcnew array<Byte>(4);
rand->NextBytes(bytes);
Console::WriteLine("Five random byte values:");
for each (Byte byteValue in bytes)
Console::Write("{0, 5}", byteValue);
Console::WriteLine();
// Generate and display 5 random integers.
Console::WriteLine("Five random integer values:");
for (int ctr = 0; ctr <= 4; ctr++)
Console::Write("{0,15:N0}", rand->Next());
Console::WriteLine();
// Generate and display 5 random integers between 0 and 100.//
Console::WriteLine("Five random integers between 0 and 100:");
for (int ctr = 0; ctr <= 4; ctr++)
Console::Write("{0,8:N0}", rand->Next(101));
Console::WriteLine();
// Generate and display 5 random integers from 50 to 100.
Console::WriteLine("Five random integers between 50 and 100:");
for (int ctr = 0; ctr <= 4; ctr++)
Console::Write("{0,8:N0}", rand->Next(50, 101));
Console::WriteLine();
// Generate and display 5 random floating point values from 0 to 1.
Console::WriteLine("Five Doubles.");
for (int ctr = 0; ctr <= 4; ctr++)
Console::Write("{0,8:N3}", rand->NextDouble());
Console::WriteLine();
// Generate and display 5 random floating point values from 0 to 5.
Console::WriteLine("Five Doubles between 0 and 5.");
for (int ctr = 0; ctr <= 4; ctr++)
Console::Write("{0,8:N3}", rand->NextDouble() * 5);
}
// The example displays output like the following:
//    Five random byte values:
//      194  185  239   54  116
//    Five random integer values:
//        507,353,531  1,509,532,693  2,125,074,958  1,409,512,757    652,767,128
//    Five random integers between 0 and 100:
//          16      78      94      79      52
//    Five random integers between 50 and 100:
//          56      66      96      60      65
//    Five Doubles.
//       0.943   0.108   0.744   0.563   0.415
//    Five Doubles between 0 and 5.
//       2.934   3.130   0.292   1.432   4.369
// Instantiate random number generator using system-supplied value as seed.
var rand = new Random();

// Generate and display 5 random byte (integer) values.
var bytes = new byte[5];
rand.NextBytes(bytes);
Console.WriteLine("Five random byte values:");
foreach (byte byteValue in bytes)
Console.Write("{0, 5}", byteValue);
Console.WriteLine();

// Generate and display 5 random integers.
Console.WriteLine("Five random integer values:");
for (int ctr = 0; ctr <= 4; ctr++)
Console.Write("{0,15:N0}", rand.Next());
Console.WriteLine();

// Generate and display 5 random integers between 0 and 100.
Console.WriteLine("Five random integers between 0 and 100:");
for (int ctr = 0; ctr <= 4; ctr++)
Console.Write("{0,8:N0}", rand.Next(101));
Console.WriteLine();

// Generate and display 5 random integers from 50 to 100.
Console.WriteLine("Five random integers between 50 and 100:");
for (int ctr = 0; ctr <= 4; ctr++)
Console.Write("{0,8:N0}", rand.Next(50, 101));
Console.WriteLine();

// Generate and display 5 random floating point values from 0 to 1.
Console.WriteLine("Five Doubles.");
for (int ctr = 0; ctr <= 4; ctr++)
Console.Write("{0,8:N3}", rand.NextDouble());
Console.WriteLine();

// Generate and display 5 random floating point values from 0 to 5.
Console.WriteLine("Five Doubles between 0 and 5.");
for (int ctr = 0; ctr <= 4; ctr++)
Console.Write("{0,8:N3}", rand.NextDouble() * 5);

// The example displays output like the following:
//    Five random byte values:
//      194  185  239   54  116
//    Five random integer values:
//        507,353,531  1,509,532,693  2,125,074,958  1,409,512,757    652,767,128
//    Five random integers between 0 and 100:
//          16      78      94      79      52
//    Five random integers between 50 and 100:
//          56      66      96      60      65
//    Five Doubles.
//       0.943   0.108   0.744   0.563   0.415
//    Five Doubles between 0 and 5.
//       2.934   3.130   0.292   1.432   4.369
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
' The example displays output like the following:
'    Five random byte values:
'      194  185  239   54  116
'    Five random integer values:
'        507,353,531  1,509,532,693  2,125,074,958  1,409,512,757    652,767,128
'    Five random integers between 0 and 100:
'          16      78      94      79      52
'    Five random integers between 50 and 100:
'          56      66      96      60      65
'    Five Doubles.
'       0.943   0.108   0.744   0.563   0.415
'    Five Doubles between 0 and 5.
'       2.934   3.130   0.292   1.432   4.369

O exemplo a seguir gera um inteiro aleatório que ele usa como um índice para recuperar um valor de cadeia de caracteres de uma matriz.The following example generates a random integer that it uses as an index to retrieve a string value from an array.

using namespace System;

void main()
{
Random^ rnd = gcnew Random();
array<String^>^ malePetNames = { "Rufus", "Bear", "Dakota", "Fido",
"Vanya", "Samuel", "Koani", "Volodya",
"Prince", "Yiska" };
array<String^>^ femalePetNames = { "Maggie", "Penny", "Saya", "Princess",
"Abby", "Laila", "Sadie", "Olivia",
"Starlight", "Talla" };

// Generate random indexes for pet names.
int mIndex = rnd->Next(malePetNames->Length);
int fIndex = 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]);
}
// The example displays output similar to the following:
//       Suggested pet name of the day:
//          For a male:     Koani
//          For a female:   Maggie
Random rnd = new Random();
string[] malePetNames = { "Rufus", "Bear", "Dakota", "Fido",
"Vanya", "Samuel", "Koani", "Volodya",
"Prince", "Yiska" };
string[] femalePetNames = { "Maggie", "Penny", "Saya", "Princess",
"Abby", "Laila", "Sadie", "Olivia",
"Starlight", "Talla" };

// Generate random indexes for pet names.
int mIndex = rnd.Next(malePetNames.Length);
int fIndex = 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]);

// The example displays output similar to the following:
//       Suggested pet name of the day:
//          For a male:     Koani
//          For a female:   Maggie
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
' The example displays output similar to the following:
'       Suggested pet name of the day:
'          For a male:     Koani
'          For a female:   Maggie

## Comentários

Números pseudo aleatórios são escolhidos com probabilidade igual de um conjunto finito de números.Pseudo-random numbers are chosen with equal probability from a finite set of numbers. Os números escolhidos não são completamente aleatórios porque um algoritmo matemático é usado para selecioná-los, mas são suficientemente aleatórios para fins práticos.The chosen numbers are not completely random because a mathematical algorithm is used to select them, but they are sufficiently random for practical purposes. A implementação atual da Random classe é baseada em uma versão modificada do algoritmo gerador de número aleatório subtraído do Donald E. Knuth.The current implementation of the Random class is based on a modified version of Donald E. Knuth's subtractive random number generator algorithm. Para obter mais informações, consulte D. E.For more information, see D. E. Knuth.Knuth. A arte de programação de computador, volume 2: algoritmos de seminumerical.The Art of Computer Programming, Volume 2: Seminumerical Algorithms. Addison-Wesley, Reading, MA, terceira edição, 1997.Addison-Wesley, Reading, MA, third edition, 1997.

Para gerar um número aleatório seguro criptograficamente, como um que seja adequado para criar uma senha aleatória, use a RNGCryptoServiceProvider classe ou derive uma classe de System.Security.Cryptography.RandomNumberGenerator .To generate a cryptographically secure random number, such as one that's suitable for creating a random password, use the RNGCryptoServiceProvider class or derive a class from System.Security.Cryptography.RandomNumberGenerator.

Neste tópico:In this topic:

### Criando uma instância do gerador de números aleatóriosInstantiating the random number generator

Você cria uma instância do gerador de números aleatórios fornecendo um valor de semente (um valor inicial para o algoritmo de geração de números pseudo aleatórios) para um Random Construtor de classe.You instantiate the random number generator by providing a seed value (a starting value for the pseudo-random number generation algorithm) to a Random class constructor. Você pode fornecer o valor de semente de forma explícita ou implícita:You can supply the seed value either explicitly or implicitly:

• O Random(Int32) construtor usa um valor de semente explícito que você fornece.The Random(Int32) constructor uses an explicit seed value that you supply.

• O Random() construtor usa o valor de semente padrão.The Random() constructor uses the default seed value. Essa é a maneira mais comum de instanciar o gerador de números aleatórios.This is the most common way of instantiating the random number generator.

No .NET Framework, o valor de semente padrão depende do tempo.In .NET Framework, the default seed value is time-dependent. No .NET Core, o valor de semente padrão é produzido pelo gerador de números pseudo aleatórios thread-estático.In .NET Core, the default seed value is produced by the thread-static, pseudo-random number generator.

Se a mesma semente for usada para Random objetos separados, elas irão gerar a mesma série de números aleatórios.If the same seed is used for separate Random objects, they will generate the same series of random numbers. Isso pode ser útil para criar um conjunto de testes que processa valores aleatórios ou para reproduzir jogos que derivam seus dados de números aleatórios.This can be useful for creating a test suite that processes random values, or for replaying games that derive their data from random numbers. No entanto, observe que Random os objetos em processos executados em versões diferentes do .NET Framework podem retornar uma série diferente de números aleatórios, mesmo que eles sejam instanciados com valores de semente idênticos.However, note that Random objects in processes running under different versions of the .NET Framework may return different series of random numbers even if they're instantiated with identical seed values.

Para produzir diferentes sequências de números aleatórios, você pode tornar o valor de semente dependente do tempo, produzindo assim uma série diferente com cada nova instância do Random .To produce different sequences of random numbers, you can make the seed value time-dependent, thereby producing a different series with each new instance of Random. O Random(Int32) Construtor com parâmetros pode usar um Int32 valor com base no número de tiques na hora atual, enquanto o construtor sem parâmetros Random() usa o relógio do sistema para gerar seu valor de semente.The parameterized Random(Int32) constructor can take an Int32 value based on the number of ticks in the current time, whereas the parameterless Random() constructor uses the system clock to generate its seed value. No entanto, somente na .NET Framework, como o relógio tem resolução finita, o uso do construtor sem parâmetros para criar Random objetos diferentes em uma sucessão de fechamento cria geradores de números aleatórios que produzem sequências idênticas de números aleatórios.However, on the .NET Framework only, because the clock has finite resolution, using the parameterless constructor to create different Random objects in close succession creates random number generators that produce identical sequences of random numbers. O exemplo a seguir ilustra como dois Random objetos que são instanciados em uma sucessão de fechamento em um aplicativo .NET Framework geram uma série idêntica de números aleatórios.The following example illustrates how two Random objects that are instantiated in close succession in a .NET Framework application generate an identical series of random numbers. Na maioria dos sistemas Windows, Random os objetos criados em 15 milissegundos um do outro provavelmente terão valores de semente idênticos.On most Windows systems, Random objects created within 15 milliseconds of one another are likely to have identical seed values.

using namespace System;

void main()
{
array<Byte>^ bytes1 = gcnew array<Byte>(100);
array<Byte>^ bytes2 = gcnew array<Byte>(100);
Random^ rnd1 = gcnew Random();
Random^ rnd2 = gcnew Random();

rnd1->NextBytes(bytes1);
rnd2->NextBytes(bytes2);

Console::WriteLine("First Series:");
for (int ctr = bytes1->GetLowerBound(0);
ctr <= bytes1->GetUpperBound(0);
ctr++) {
Console::Write("{0, 5}", bytes1[ctr]);
if ((ctr + 1) % 10 == 0) Console::WriteLine();
}
Console::WriteLine();
Console::WriteLine("Second Series:");
for (int ctr = bytes2->GetLowerBound(0);
ctr <= bytes2->GetUpperBound(0);
ctr++) {
Console::Write("{0, 5}", bytes2[ctr]);
if ((ctr + 1) % 10 == 0) Console::WriteLine();
}
}
// The example displays output like the following:
//       First Series:
//          97  129  149   54   22  208  120  105   68  177
//         113  214   30  172   74  218  116  230   89   18
//          12  112  130  105  116  180  190  200  187  120
//           7  198  233  158   58   51   50  170   98   23
//          21    1  113   74  146  245   34  255   96   24
//         232  255   23    9  167  240  255   44  194   98
//          18  175  173  204  169  171  236  127  114   23
//         167  202  132   65  253   11  254   56  214  127
//         145  191  104  163  143    7  174  224  247   73
//          52    6  231  255    5  101   83  165  160  231
//
//       Second Series:
//          97  129  149   54   22  208  120  105   68  177
//         113  214   30  172   74  218  116  230   89   18
//          12  112  130  105  116  180  190  200  187  120
//           7  198  233  158   58   51   50  170   98   23
//          21    1  113   74  146  245   34  255   96   24
//         232  255   23    9  167  240  255   44  194   98
//          18  175  173  204  169  171  236  127  114   23
//         167  202  132   65  253   11  254   56  214  127
//         145  191  104  163  143    7  174  224  247   73
//          52    6  231  255    5  101   83  165  160  231
byte[] bytes1 = new byte[100];
byte[] bytes2 = new byte[100];
Random rnd1 = new Random();
Random rnd2 = new Random();

rnd1.NextBytes(bytes1);
rnd2.NextBytes(bytes2);

Console.WriteLine("First Series:");
for (int ctr = bytes1.GetLowerBound(0);
ctr <= bytes1.GetUpperBound(0);
ctr++) {
Console.Write("{0, 5}", bytes1[ctr]);
if ((ctr + 1) % 10 == 0) Console.WriteLine();
}

Console.WriteLine();

Console.WriteLine("Second Series:");
for (int ctr = bytes2.GetLowerBound(0);
ctr <= bytes2.GetUpperBound(0);
ctr++) {
Console.Write("{0, 5}", bytes2[ctr]);
if ((ctr + 1) % 10 == 0) Console.WriteLine();
}

// The example displays output like the following:
//       First Series:
//          97  129  149   54   22  208  120  105   68  177
//         113  214   30  172   74  218  116  230   89   18
//          12  112  130  105  116  180  190  200  187  120
//           7  198  233  158   58   51   50  170   98   23
//          21    1  113   74  146  245   34  255   96   24
//         232  255   23    9  167  240  255   44  194   98
//          18  175  173  204  169  171  236  127  114   23
//         167  202  132   65  253   11  254   56  214  127
//         145  191  104  163  143    7  174  224  247   73
//          52    6  231  255    5  101   83  165  160  231
//
//       Second Series:
//          97  129  149   54   22  208  120  105   68  177
//         113  214   30  172   74  218  116  230   89   18
//          12  112  130  105  116  180  190  200  187  120
//           7  198  233  158   58   51   50  170   98   23
//          21    1  113   74  146  245   34  255   96   24
//         232  255   23    9  167  240  255   44  194   98
//          18  175  173  204  169  171  236  127  114   23
//         167  202  132   65  253   11  254   56  214  127
//         145  191  104  163  143    7  174  224  247   73
//          52    6  231  255    5  101   83  165  160  231
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
' The example displays output like the following:
'       First Series:
'          97  129  149   54   22  208  120  105   68  177
'         113  214   30  172   74  218  116  230   89   18
'          12  112  130  105  116  180  190  200  187  120
'           7  198  233  158   58   51   50  170   98   23
'          21    1  113   74  146  245   34  255   96   24
'         232  255   23    9  167  240  255   44  194   98
'          18  175  173  204  169  171  236  127  114   23
'         167  202  132   65  253   11  254   56  214  127
'         145  191  104  163  143    7  174  224  247   73
'          52    6  231  255    5  101   83  165  160  231
'
'       Second Series:
'          97  129  149   54   22  208  120  105   68  177
'         113  214   30  172   74  218  116  230   89   18
'          12  112  130  105  116  180  190  200  187  120
'           7  198  233  158   58   51   50  170   98   23
'          21    1  113   74  146  245   34  255   96   24
'         232  255   23    9  167  240  255   44  194   98
'          18  175  173  204  169  171  236  127  114   23
'         167  202  132   65  253   11  254   56  214  127
'         145  191  104  163  143    7  174  224  247   73
'          52    6  231  255    5  101   83  165  160  231

Para evitar esse problema, crie um único Random objeto em vez de vários objetos.To avoid this problem, create a single Random object instead of multiple objects. Observe que a Random classe no .NET Core não tem essa limitação.Note that the Random class in .NET Core does not have this limitation.

### Evitando várias instanciaçõesAvoiding multiple instantiations

Na .NET Framework, inicializar dois geradores de número aleatório em um loop rígido ou em uma sucessão rápida cria dois geradores de números aleatórios que podem produzir sequências idênticas de números aleatórios.On the .NET Framework, initializing two random number generators in a tight loop or in rapid succession creates two random number generators that can produce identical sequences of random numbers. Na maioria dos casos, essa não é a intenção do desenvolvedor e pode levar a problemas de desempenho, pois instanciar e inicializar um gerador de números aleatórios é um processo relativamente caro.In most cases, this is not the developer's intent and can lead to performance issues, because instantiating and initializing a random number generator is a relatively expensive process.

Para melhorar o desempenho e evitar criar inadvertidamente geradores de números aleatórios separados que geram sequências numéricas idênticas, recomendamos que você crie um Random objeto para gerar muitos números aleatórios ao longo do tempo, em vez de criar novos Random objetos para gerar um número aleatório.Both to improve performance and to avoid inadvertently creating separate random number generators that generate identical numeric sequences, we recommend that you create one Random object to generate many random numbers over time, instead of creating new Random objects to generate one random number.

No entanto, a Random classe não é thread-safe.However, the Random class isn't thread safe. Se você chamar Random métodos de vários threads, siga as diretrizes discutidas na próxima seção.If you call Random methods from multiple threads, follow the guidelines discussed in the next section.

### A classe System. Random e a segurança do threadThe System.Random class and thread safety

Em vez de instanciar Random objetos individuais, recomendamos que você crie uma única Random instância para gerar todos os números aleatórios necessários para seu aplicativo.Instead of instantiating individual Random objects, we recommend that you create a single Random instance to generate all the random numbers needed by your app. No entanto, os Random objetos não são thread-safe.However, Random objects are not thread safe. Se seu aplicativo chama Random métodos de vários threads, você deve usar um objeto de sincronização para garantir que apenas um thread possa acessar o gerador de números aleatórios de cada vez.If your app calls Random methods from multiple threads, you must use a synchronization object to ensure that only one thread can access the random number generator at a time. Se você não garantir que o Random objeto seja acessado de forma segura para thread, as chamadas para métodos que retornam números aleatórios retornam 0.If you don't ensure that the Random object is accessed in a thread-safe way, calls to methods that return random numbers return 0.

O exemplo a seguir usa a instrução Lock do C# e a instrução Visual Basic SyncLock para garantir que um único gerador de número aleatório seja acessado por 11 threads de forma segura para thread.The following example uses the C# lock Statement and the Visual Basic SyncLock statement to ensure that a single random number generator is accessed by 11 threads in a thread-safe manner. Cada thread gera 2 milhões números aleatórios, conta o número de números aleatórios gerados e calcula a soma e, em seguida, atualiza os totais de todos os threads quando ele termina a execução.Each thread generates 2 million random numbers, counts the number of random numbers generated and calculates their sum, and then updates the totals for all threads when it finishes executing.

using namespace System;
using namespace System::Threading;

ref class Example
{
private:
[ThreadStatic] static double previous = 0.0;
[ThreadStatic] static int perThreadCtr = 0;
[ThreadStatic] static double perThreadTotal = 0.0;
static CancellationTokenSource^ source;
static CountdownEvent^ countdown;
static Object^ randLock;
static Object^ numericLock;
static Random^ rand;
double totalValue = 0.0;
int totalCount = 0;

public:
Example()
{
rand = gcnew Random();
randLock = gcnew Object();
numericLock = gcnew Object();
countdown = gcnew CountdownEvent(1);
source = gcnew CancellationTokenSource();
}

void Execute()
{
CancellationToken^ token = source->Token;

for (int threads = 1; threads <= 10; threads++)
{
Thread^ newThread = gcnew Thread(gcnew ParameterizedThreadStart(this, &Example::GetRandomNumbers));
newThread->Name = threads.ToString();
newThread->Start(token);
}
this->GetRandomNumbers(token);

countdown->Signal();
// Make sure all threads have finished.
countdown->Wait();

Console::WriteLine("\nTotal 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);
}

private:
void GetRandomNumbers(Object^ o)
{
CancellationToken^ token = (CancellationToken) o;
double result = 0.0;
countdown->AddCount(1);

try {
for (int ctr = 0; ctr < 2000000; ctr++)
{
// Make sure there's no corruption of Random.
token->ThrowIfCancellationRequested();

Monitor::Enter(randLock);
result = rand->NextDouble();
Monitor::Exit(randLock);
// Check for corruption of Random instance.
if ((result == previous) && result == 0) {
source->Cancel();
}
else {
previous = result;
}
perThreadCtr++;
perThreadTotal += result;
}

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}\n", perThreadTotal/perThreadCtr);

// Update overall totals.
Monitor::Enter(numericLock);
totalCount += perThreadCtr;
totalValue += perThreadTotal;
Monitor::Exit(numericLock);
}
catch (OperationCanceledException^ e) {
Console::WriteLine("Corruption in Thread {1}", e->GetType()->Name,
Thread::CurrentThread->Name);
}
finally {
countdown->Signal();
}
}
};

void main()
{
Example^ ex = gcnew Example();
Thread::CurrentThread->Name = "Main";
ex->Execute();
}
// The example displays output like the following:
//       Thread 6 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,491.05
//       Random number mean: 0.5002
//
//       Thread 10 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,329.64
//       Random number mean: 0.4997
//
//       Thread 4 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,166.89
//       Random number mean: 0.5001
//
//       Thread 8 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,628.37
//       Random number mean: 0.4998
//
//       Thread Main finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,920.89
//       Random number mean: 0.5000
//
//       Thread 3 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,370.45
//       Random number mean: 0.4997
//
//       Thread 7 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,330.92
//       Random number mean: 0.4997
//
//       Thread 9 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,172.79
//       Random number mean: 0.5001
//
//       Thread 5 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,079.43
//       Random number mean: 0.5000
//
//       Thread 1 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,817.91
//       Random number mean: 0.4999
//
//       Thread 2 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,930.63
//       Random number mean: 0.5000
//
//
//       Total random numbers generated: 22,000,000
//       Total sum of all random numbers: 10,998,238.98
//       Random number mean: 0.4999
using System;
using System.Threading;

public class Example
{
[ThreadStatic] static double previous = 0.0;
[ThreadStatic] static int perThreadCtr = 0;
[ThreadStatic] static double perThreadTotal = 0.0;
static CancellationTokenSource source;
static CountdownEvent countdown;
static Object randLock, numericLock;
static Random rand;
double totalValue = 0.0;
int totalCount = 0;

public Example()
{
rand = new Random();
randLock = new Object();
numericLock = new Object();
countdown = new CountdownEvent(1);
source = new CancellationTokenSource();
}

public static void Main()
{
Example ex = new Example();
Thread.CurrentThread.Name = "Main";
ex.Execute();
}

private void Execute()
{
CancellationToken token = source.Token;

for (int threads = 1; threads <= 10; threads++)
{
Thread newThread = new Thread(this.GetRandomNumbers);
newThread.Name = threads.ToString();
newThread.Start(token);
}
this.GetRandomNumbers(token);

countdown.Signal();
// Make sure all threads have finished.
countdown.Wait();
source.Dispose();

Console.WriteLine("\nTotal 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);
}

private void GetRandomNumbers(Object o)
{
CancellationToken token = (CancellationToken) o;
double result = 0.0;
countdown.AddCount(1);

try {
for (int ctr = 0; ctr < 2000000; ctr++)
{
// Make sure there's no corruption of Random.
token.ThrowIfCancellationRequested();

lock (randLock) {
result = rand.NextDouble();
}
// Check for corruption of Random instance.
if ((result == previous) && result == 0) {
source.Cancel();
}
else {
previous = result;
}
perThreadCtr++;
perThreadTotal += result;
}

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}\n", perThreadTotal/perThreadCtr);

// Update overall totals.
lock (numericLock) {
totalCount += perThreadCtr;
totalValue += perThreadTotal;
}
}
catch (OperationCanceledException e) {
Console.WriteLine("Corruption in Thread {1}", e.GetType().Name, Thread.CurrentThread.Name);
}
finally {
countdown.Signal();
}
}
}
// The example displays output like the following:
//       Thread 6 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,491.05
//       Random number mean: 0.5002
//
//       Thread 10 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,329.64
//       Random number mean: 0.4997
//
//       Thread 4 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,166.89
//       Random number mean: 0.5001
//
//       Thread 8 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,628.37
//       Random number mean: 0.4998
//
//       Thread Main finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,920.89
//       Random number mean: 0.5000
//
//       Thread 3 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,370.45
//       Random number mean: 0.4997
//
//       Thread 7 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,330.92
//       Random number mean: 0.4997
//
//       Thread 9 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,172.79
//       Random number mean: 0.5001
//
//       Thread 5 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,079.43
//       Random number mean: 0.5000
//
//       Thread 1 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,817.91
//       Random number mean: 0.4999
//
//       Thread 2 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,930.63
//       Random number mean: 0.5000
//
//
//       Total random numbers generated: 22,000,000
//       Total sum of all random numbers: 10,998,238.98
//       Random number mean: 0.4999
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
' The example displays output like the following:
'       Thread 6 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 1,000,491.05
'       Random number mean: 0.5002
'
'       Thread 10 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 999,329.64
'       Random number mean: 0.4997
'
'       Thread 4 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 1,000,166.89
'       Random number mean: 0.5001
'
'       Thread 8 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 999,628.37
'       Random number mean: 0.4998
'
'       Thread Main finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 999,920.89
'       Random number mean: 0.5000
'
'       Thread 3 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 999,370.45
'       Random number mean: 0.4997
'
'       Thread 7 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 999,330.92
'       Random number mean: 0.4997
'
'       Thread 9 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 1,000,172.79
'       Random number mean: 0.5001
'
'       Thread 5 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 1,000,079.43
'       Random number mean: 0.5000
'
'       Thread 1 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 999,817.91
'       Random number mean: 0.4999
'
'       Thread 2 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 999,930.63
'       Random number mean: 0.5000
'
'
'       Total random numbers generated: 22,000,000
'       Total sum of all random numbers: 10,998,238.98
'       Random number mean: 0.4999

O exemplo garante a segurança de thread das seguintes maneiras:The example ensures thread-safety in the following ways:

• O ThreadStaticAttribute atributo é usado para definir variáveis de local de thread que acompanham o número total de números aleatórios gerados e sua soma para cada thread.The ThreadStaticAttribute attribute is used to define thread-local variables that track the total number of random numbers generated and their sum for each thread.

• Um bloqueio (a lock instrução em C# e a SyncLock instrução em Visual Basic) protege o acesso às variáveis para a contagem total e a soma de todos os números aleatórios gerados em todos os threads.A lock (the lock statement in C# and the SyncLock statement in Visual Basic) protects access to the variables for the total count and sum of all random numbers generated on all threads.

• Um semáforo (o CountdownEvent objeto) é usado para garantir que o thread principal seja bloqueado até que todos os outros threads concluam a execução.A semaphore (the CountdownEvent object) is used to ensure that the main thread blocks until all other threads complete execution.

• O exemplo verifica se o gerador de números aleatórios se tornou corrompido determinando se duas chamadas consecutivas para métodos de geração de números aleatórios retornam 0.The example checks whether the random number generator has become corrupted by determining whether two consecutive calls to random number generation methods return 0. Se a corrupção for detectada, o exemplo usará o CancellationTokenSource objeto para sinalizar que todos os threads devem ser cancelados.If corruption is detected, the example uses the CancellationTokenSource object to signal that all threads should be canceled.

• Antes de gerar cada número aleatório, cada thread verifica o estado do CancellationToken objeto.Before generating each random number, each thread checks the state of the CancellationToken object. Se o cancelamento for solicitado, o exemplo chamará o CancellationToken.ThrowIfCancellationRequested método para cancelar o thread.If cancellation is requested, the example calls the CancellationToken.ThrowIfCancellationRequested method to cancel the thread.

O exemplo a seguir é idêntico ao primeiro, exceto pelo fato de que ele usa um Task objeto e uma expressão lambda em vez de Thread objetos.The following example is identical to the first, except that it uses a Task object and a lambda expression instead of Thread objects.

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
static Object randLock, numericLock;
static Random rand;
static CancellationTokenSource source;
double totalValue = 0.0;
int totalCount = 0;

public Example()
{
rand = new Random();
randLock = new Object();
numericLock = new Object();
source = new CancellationTokenSource();
}

public static async Task Main()
{
Example ex = new Example();
Thread.CurrentThread.Name = "Main";
await ex.Execute();
}

private Task Execute()
{
List<Task> tasks = new List<Task>();

for (int ctr = 0; ctr <= 10; ctr++)
{
CancellationToken token = source.Token;
int taskNo = ctr;
tasks.Add(Task.Run( () =>
{
double previous = 0.0;
int taskCtr = 0;
double taskTotal = 0.0;
double result = 0.0;

for (int n = 0; n < 2000000; n++)
{
// Make sure there's no corruption of Random.
token.ThrowIfCancellationRequested();

lock (randLock) {
result = rand.NextDouble();
}
// Check for corruption of Random instance.
if ((result == previous) && result == 0) {
source.Cancel();
}
else {
previous = result;
}
taskCtr++;
taskTotal += result;
}

// 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}\n", taskTotal/taskCtr);

// Update overall totals.
lock (numericLock) {
totalCount += taskCtr;
totalValue += taskTotal;
}
},
token));
}
try {
await Task.WhenAll(tasks.ToArray());
Console.WriteLine("\nTotal 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 (AggregateException e) {
foreach (Exception inner in e.InnerExceptions) {
TaskCanceledException canc = inner as TaskCanceledException;
if (canc != null)
Console.WriteLine("Task #{0} cancelled.", canc.Task.Id);
else
Console.WriteLine("Exception: {0}", inner.GetType().Name);
}
}
finally {
source.Dispose();
}
}
}
// The example displays output like the following:
//       Task 1 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,502.47
//       Random number mean: 0.5003
//
//       Task 0 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,445.63
//       Random number mean: 0.5002
//
//       Task 2 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,556.04
//       Random number mean: 0.5003
//
//       Task 3 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,178.87
//       Random number mean: 0.5001
//
//       Task 4 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,819.17
//       Random number mean: 0.4999
//
//       Task 5 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,190.58
//       Random number mean: 0.5001
//
//       Task 6 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,720.21
//       Random number mean: 0.4999
//
//       Task 7 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,000.96
//       Random number mean: 0.4995
//
//       Task 8 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,499.33
//       Random number mean: 0.4997
//
//       Task 9 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 1,000,193.25
//       Random number mean: 0.5001
//
//       Task 10 finished execution.
//       Random numbers generated: 2,000,000
//       Sum of random numbers: 999,960.82
//       Random number mean: 0.5000
//
//
//       Total random numbers generated: 22,000,000
//       Total sum of all random numbers: 11,000,067.33
//       Random number mean: 0.5000
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
' The example displays output like the following:
'       Task 1 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 1,000,502.47
'       Random number mean: 0.5003
'
'       Task 0 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 1,000,445.63
'       Random number mean: 0.5002
'
'       Task 2 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 1,000,556.04
'       Random number mean: 0.5003
'
'       Task 3 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 1,000,178.87
'       Random number mean: 0.5001
'
'       Task 4 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 999,819.17
'       Random number mean: 0.4999
'
'       Task 5 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 1,000,190.58
'       Random number mean: 0.5001
'
'       Task 6 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 999,720.21
'       Random number mean: 0.4999
'
'       Task 7 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 999,000.96
'       Random number mean: 0.4995
'
'       Task 8 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 999,499.33
'       Random number mean: 0.4997
'
'       Task 9 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 1,000,193.25
'       Random number mean: 0.5001
'
'       Task 10 finished execution.
'       Random numbers generated: 2,000,000
'       Sum of random numbers: 999,960.82
'       Random number mean: 0.5000
'
'
'       Total random numbers generated: 22,000,000
'       Total sum of all random numbers: 11,000,067.33
'       Random number mean: 0.5000

Ele difere do primeiro exemplo das seguintes maneiras:It differs from the first example in the following ways:

• As variáveis para acompanhar o número de números aleatórios gerados e sua soma em cada tarefa são locais para a tarefa, portanto, não é necessário usar o ThreadStaticAttribute atributo.The variables to keep track of the number of random numbers generated and their sum in each task are local to the task, so there is no need to use the ThreadStaticAttribute attribute.

• O Task.WaitAll método estático é usado para garantir que o thread principal não seja concluído antes que todas as tarefas sejam concluídas.The static Task.WaitAll method is used to ensure that the main thread doesn't complete before all tasks have finished. Não há necessidade do CountdownEvent objeto.There is no need for the CountdownEvent object.

• A exceção resultante do cancelamento da tarefa é superficial no Task.WaitAll método.The exception that results from task cancellation is surfaced in the Task.WaitAll method. No exemplo anterior, ele é manipulado por cada thread.In the previous example, it is handled by each thread.

### Gerando tipos diferentes de números aleatóriosGenerating different types of random numbers

O gerador de número aleatório fornece métodos que permitem gerar os seguintes tipos de números aleatórios:The random number generator provides methods that let you generate the following kinds of random numbers:

• Uma série de Byte valores.A series of Byte values. Você determina o número de valores de byte passando uma matriz inicializada para o número de elementos que você deseja que o método retorne ao NextBytes método.You determine the number of byte values by passing an array initialized to the number of elements you want the method to return to the NextBytes method. O exemplo a seguir gera 20 bytes.The following example generates 20 bytes.

using namespace System;

void main()
{
Random^ rnd = gcnew Random();
array<Byte>^ bytes = gcnew array<Byte>(20);
rnd->NextBytes(bytes);
for (int ctr = 1; ctr <= bytes->Length; ctr++) {
Console::Write("{0,3}   ", bytes[ctr - 1]);
if (ctr % 10 == 0) Console::WriteLine();
}
}
// The example displays output like the following:
//       141    48   189    66   134   212   211    71   161    56
//       181   166   220   133     9   252   222    57    62    62

Random rnd = new Random();
Byte[] bytes = new Byte[20];
rnd.NextBytes(bytes);
for (int ctr = 1; ctr <= bytes.Length; ctr++) {
Console.Write("{0,3}   ", bytes[ctr - 1]);
if (ctr % 10 == 0) Console.WriteLine();
}

// The example displays output like the following:
//       141    48   189    66   134   212   211    71   161    56
//       181   166   220   133     9   252   222    57    62    62

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
' The example displays output like the following:
'       141    48   189    66   134   212   211    71   161    56
'       181   166   220   133     9   252   222    57    62    62

• Um único inteiro.A single integer. Você pode escolher se deseja um inteiro de 0 a um valor máximo ( Int32.MaxValue -1) chamando o Next() método, um inteiro entre 0 e um valor específico chamando o Next(Int32) método ou um inteiro em um intervalo de valores chamando o Next(Int32, Int32) método.You can choose whether you want an integer from 0 to a maximum value (Int32.MaxValue - 1) by calling the Next() method, an integer between 0 and a specific value by calling the Next(Int32) method, or an integer within a range of values by calling the Next(Int32, Int32) method. Nas sobrecargas parametrizadas, o valor máximo especificado é exclusivo; ou seja, o número máximo real gerado é um valor menor que o especificado.In the parameterized overloads, the specified maximum value is exclusive; that is, the actual maximum number generated is one less than the specified value.

O exemplo a seguir chama o Next(Int32, Int32) método para gerar 10 números aleatórios entre-10 e 10.The following example calls the Next(Int32, Int32) method to generate 10 random numbers between -10 and 10. Observe que o segundo argumento para o método especifica o limite superior exclusivo do intervalo de valores aleatórios retornados pelo método.Note that the second argument to the method specifies the exclusive upper bound of the range of random values returned by the method. Em outras palavras, o maior número inteiro que o método pode retornar é um valor menor que esse.In other words, the largest integer that the method can return is one less than this value.

using namespace System;

void main()
{
Random^ rnd = gcnew Random();
for (int ctr = 0; ctr < 10; ctr++) {
Console::Write("{0,3}   ", rnd->Next(-10, 11));
}
}
// The example displays output like the following:
//    2     9    -3     2     4    -7    -3    -8    -8     5

Random rnd = new Random();
for (int ctr = 0; ctr < 10; ctr++) {
Console.Write("{0,3}   ", rnd.Next(-10, 11));
}

// The example displays output like the following:
//    2     9    -3     2     4    -7    -3    -8    -8     5

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
' The example displays output like the following:
'    2     9    -3     2     4    -7    -3    -8    -8     5

• Um único valor de ponto flutuante de 0,0 para menor que 1,0 chamando o NextDouble método.A single floating-point value from 0.0 to less than 1.0 by calling the NextDouble method. O limite superior exclusivo do número aleatório retornado pelo método é 1, portanto, seu limite superior real é 0.99999999999999978.The exclusive upper bound of the random number returned by the method is 1, so its actual upper bound is 0.99999999999999978. O exemplo a seguir gera 10 números de ponto flutuante aleatório.The following example generates 10 random floating-point numbers.

using namespace System;

void main()
{
Random^ rnd = gcnew Random();
for (int ctr = 0; ctr < 10; ctr++) {
Console::Write("{0,-19:R}   ", rnd->NextDouble());
if ((ctr + 1) % 3 == 0) Console::WriteLine();
}
}
// The example displays output like the following:
//    0.7911680553998649    0.0903414949264105    0.79776258291572455
//    0.615568345233597     0.652644504165577     0.84023809378977776
//    0.099662564741290441   0.91341467383942321  0.96018602045261581
//    0.74772306473354022

Random rnd = new Random();
for (int ctr = 0; ctr < 10; ctr++) {
Console.Write("{0,-19:R}   ", rnd.NextDouble());
if ((ctr + 1) % 3 == 0) Console.WriteLine();
}

// The example displays output like the following:
//    0.7911680553998649    0.0903414949264105    0.79776258291572455
//    0.615568345233597     0.652644504165577     0.84023809378977776
//    0.099662564741290441   0.91341467383942321  0.96018602045261581
//    0.74772306473354022

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
' The example displays output like the following:
'    0.7911680553998649    0.0903414949264105    0.79776258291572455
'    0.615568345233597     0.652644504165577     0.84023809378977776
'    0.099662564741290441  0.91341467383942321   0.96018602045261581
'    0.74772306473354022

Importante

O Next(Int32, Int32) método permite que você especifique o intervalo do número aleatório retornado.The Next(Int32, Int32) method allows you to specify the range of the returned random number. No entanto, o maxValue parâmetro, que especifica o número do intervalo superior retornado, é um valor exclusivo, e não inclusivo.However, the maxValue parameter, which specifies the upper range returned number, is an exclusive, not an inclusive, value. Isso significa que a chamada do método Next(0, 100) retorna um valor entre 0 e 99, e não entre 0 e 100.This means that the method call Next(0, 100) returns a value between 0 and 99, and not between 0 and 100.

Você também pode usar a Random classe para tarefas como gerar valores de T:System.Boolean aleatórios, gerando valores de ponto flutuante aleatório com um intervalo diferente de 0 a 1, gerando inteiros aleatórios de 64 bitse recuperando aleatoriamente um elemento exclusivo de uma matriz ou coleção.You can also use the Random class for such tasks as generating random T:System.Boolean values, generating random floating point values with a range other than 0 to 1, generating random 64-bit integers, and randomly retrieving a unique element from an array or collection. Para essas e outras tarefas comuns, consulte como usar o System. Random para.. .For these and other common tasks, see the How do you use System.Random to… seção.section.

### Substituindo seu próprio algoritmoSubstituting your own algorithm

Você pode implementar seu próprio gerador de números aleatórios herdando da Random classe e fornecendo seu algoritmo de geração de números aleatórios.You can implement your own random number generator by inheriting from the Random class and supplying your random number generation algorithm. Para fornecer seu próprio algoritmo, você deve substituir o Sample método, que implementa o algoritmo de geração de números aleatórios.To supply your own algorithm, you must override the Sample method, which implements the random number generation algorithm. Você também deve substituir os Next() Next(Int32, Int32) métodos, e NextBytes para garantir que eles chamem o Sample método substituído.You should also override the Next(), Next(Int32, Int32), and NextBytes methods to ensure that they call your overridden Sample method. Você não precisa substituir os Next(Int32) métodos e NextDouble .You don't have to override the Next(Int32) and NextDouble methods.

Para obter um exemplo que deriva da Random classe e modifica seu gerador de números pseudo aleatórios padrão, consulte a Sample página de referência.For an example that derives from the Random class and modifies its default pseudo-random number generator, see the Sample reference page.

### Como usar System. Random para...How do you use System.Random to…

As seções a seguir discutem e fornecem código de exemplo para algumas das maneiras que você pode querer usar números aleatórios em seu aplicativo.The following sections discuss and provide sample code for some of the ways you might want to use random numbers in your app.

#### Recuperar a mesma sequência de valores aleatóriosRetrieve the same sequence of random values

Às vezes, você deseja gerar a mesma sequência de números aleatórios em cenários de teste de software e em jogo.Sometimes you want to generate the same sequence of random numbers in software test scenarios and in game playing. O teste com a mesma sequência de números aleatórios permite detectar regressões e confirmar correções de bugs.Testing with the same sequence of random numbers allows you to detect regressions and confirm bug fixes. Usar a mesma sequência de número aleatório em jogos permite que você reproduza jogos anteriores.Using the same sequence of random number in games allows you to replay previous games.

Você pode gerar a mesma sequência de números aleatórios fornecendo o mesmo valor de semente ao Random(Int32) Construtor.You can generate the same sequence of random numbers by providing the same seed value to the Random(Int32) constructor. O valor de semente fornece um valor inicial para o algoritmo de geração de números pseudo aleatórios.The seed value provides a starting value for the pseudo-random number generation algorithm. O exemplo a seguir usa 100100 como um valor de semente arbitrária para instanciar o Random objeto, exibe 20 valores de ponto flutuante aleatório e persiste o valor semente.The following example uses 100100 as an arbitrary seed value to instantiate the Random object, displays 20 random floating-point values, and persists the seed value. Em seguida, ele restaura o valor semente, cria uma instância de um novo gerador de números aleatórios e exibe os mesmos 20 valores aleatórios de ponto flutuante.It then restores the seed value, instantiates a new random number generator, and displays the same 20 random floating-point values. Observe que o exemplo pode produzir sequências diferentes de números aleatórios se forem executados em versões diferentes do .NET Framework.Note that the example may produce different sequences of random numbers if run on different versions of the .NET Framework.

using System;
using System.IO;

public class Example
{
public static void Main()
{
int seed = 100100;
ShowRandomNumbers(seed);
Console.WriteLine();

PersistSeed(seed);

DisplayNewRandomNumbers();
}

private static void ShowRandomNumbers(int seed)
{
Random rnd = new Random(seed);
for (int ctr = 0; ctr <= 20; ctr++)
Console.WriteLine(rnd.NextDouble());
}

private static void PersistSeed(int seed)
{
FileStream fs = new FileStream(@".\seed.dat", FileMode.Create);
BinaryWriter bin = new BinaryWriter(fs);
bin.Write(seed);
bin.Close();
}

private static void DisplayNewRandomNumbers()
{
FileStream fs = new FileStream(@".\seed.dat", FileMode.Open);
BinaryReader bin = new BinaryReader(fs);
int seed = bin.ReadInt32();
bin.Close();

Random rnd = new Random(seed);
for (int ctr = 0; ctr <= 20; ctr++)
Console.WriteLine(rnd.NextDouble());
}
}
// The example displays output like the following:
//       0.500193602172748
//       0.0209461245783354
//       0.465869495396442
//       0.195512794514891
//       0.928583675496552
//       0.729333720509584
//       0.381455668891527
//       0.0508996467343064
//       0.019261200921266
//       0.258578445417145
//       0.0177532266908107
//       0.983277184415272
//       0.483650274334313
//       0.0219647376900375
//       0.165910115077118
//       0.572085966622497
//       0.805291457942357
//       0.927985211335116
//       0.4228545699375
//       0.523320379910674
//       0.157783938645285
//
//       0.500193602172748
//       0.0209461245783354
//       0.465869495396442
//       0.195512794514891
//       0.928583675496552
//       0.729333720509584
//       0.381455668891527
//       0.0508996467343064
//       0.019261200921266
//       0.258578445417145
//       0.0177532266908107
//       0.983277184415272
//       0.483650274334313
//       0.0219647376900375
//       0.165910115077118
//       0.572085966622497
//       0.805291457942357
//       0.927985211335116
//       0.4228545699375
//       0.523320379910674
//       0.157783938645285
using namespace System;
using namespace System::IO;

ref class RandomMethods
{
internal:
static void ShowRandomNumbers(int seed)
{
Random^ rnd = gcnew Random(seed);
for (int ctr = 0; ctr <= 20; ctr++)
Console::WriteLine(rnd->NextDouble());
}

static void PersistSeed(int seed)
{
FileStream^ fs = gcnew FileStream(".\\seed.dat", FileMode::Create);
BinaryWriter^ bin = gcnew BinaryWriter(fs);
bin->Write(seed);
bin->Close();
}

static void DisplayNewRandomNumbers()
{
FileStream^ fs = gcnew FileStream(".\\seed.dat", FileMode::Open);
BinaryReader^ bin = gcnew BinaryReader(fs);
int seed = bin->ReadInt32();
bin->Close();

Random^ rnd = gcnew Random(seed);
for (int ctr = 0; ctr <= 20; ctr++)
Console::WriteLine(rnd->NextDouble());
}
};

void main()
{
int seed = 100100;
RandomMethods::ShowRandomNumbers(seed);
Console::WriteLine();

RandomMethods::PersistSeed(seed);

RandomMethods::DisplayNewRandomNumbers();
}
// The example displays output like the following:
//       0.500193602172748
//       0.0209461245783354
//       0.465869495396442
//       0.195512794514891
//       0.928583675496552
//       0.729333720509584
//       0.381455668891527
//       0.0508996467343064
//       0.019261200921266
//       0.258578445417145
//       0.0177532266908107
//       0.983277184415272
//       0.483650274334313
//       0.0219647376900375
//       0.165910115077118
//       0.572085966622497
//       0.805291457942357
//       0.927985211335116
//       0.4228545699375
//       0.523320379910674
//       0.157783938645285
//
//       0.500193602172748
//       0.0209461245783354
//       0.465869495396442
//       0.195512794514891
//       0.928583675496552
//       0.729333720509584
//       0.381455668891527
//       0.0508996467343064
//       0.019261200921266
//       0.258578445417145
//       0.0177532266908107
//       0.983277184415272
//       0.483650274334313
//       0.0219647376900375
//       0.165910115077118
//       0.572085966622497
//       0.805291457942357
//       0.927985211335116
//       0.4228545699375
//       0.523320379910674
//       0.157783938645285
Imports System.IO

Module Example
Public Sub Main()
Dim seed As Integer = 100100
ShowRandomNumbers(seed)
Console.WriteLine()

PersistSeed(seed)

DisplayNewRandomNumbers()
End Sub

Private Sub ShowRandomNumbers(seed As Integer)
Dim rnd As New Random(seed)
For ctr As Integer = 0 To 20
Console.WriteLine(rnd.NextDouble())
Next
End Sub

Private Sub PersistSeed(seed As Integer)
Dim fs As New FileStream(".\seed.dat", FileMode.Create)
Dim bin As New BinaryWriter(fs)
bin.Write(seed)
bin.Close()
End Sub

Private Sub DisplayNewRandomNumbers()
Dim fs As New FileStream(".\seed.dat", FileMode.Open)
Dim bin As New BinaryReader(fs)
Dim seed As Integer = bin.ReadInt32()
bin.Close()

Dim rnd As New Random(seed)
For ctr As Integer = 0 To 20
Console.WriteLine(rnd.NextDouble())
Next
End Sub
End Module
' The example displays output like the following:
'       0.500193602172748
'       0.0209461245783354
'       0.465869495396442
'       0.195512794514891
'       0.928583675496552
'       0.729333720509584
'       0.381455668891527
'       0.0508996467343064
'       0.019261200921266
'       0.258578445417145
'       0.0177532266908107
'       0.983277184415272
'       0.483650274334313
'       0.0219647376900375
'       0.165910115077118
'       0.572085966622497
'       0.805291457942357
'       0.927985211335116
'       0.4228545699375
'       0.523320379910674
'       0.157783938645285
'
'       0.500193602172748
'       0.0209461245783354
'       0.465869495396442
'       0.195512794514891
'       0.928583675496552
'       0.729333720509584
'       0.381455668891527
'       0.0508996467343064
'       0.019261200921266
'       0.258578445417145
'       0.0177532266908107
'       0.983277184415272
'       0.483650274334313
'       0.0219647376900375
'       0.165910115077118
'       0.572085966622497
'       0.805291457942357
'       0.927985211335116
'       0.4228545699375
'       0.523320379910674
'       0.157783938645285

#### Recuperar sequências exclusivas de números aleatóriosRetrieve unique sequences of random numbers

Fornecer valores de semente diferentes para instâncias da Random classe faz com que cada gerador de números aleatórios produza uma sequência de valores diferente.Providing different seed values to instances of the Random class causes each random number generator to produce a different sequence of values. Você pode fornecer um valor de semente explicitamente chamando o Random(Int32) Construtor ou implicitamente chamando o Random() Construtor.You can provide a seed value either explicitly by calling the Random(Int32) constructor, or implicitly by calling the Random() constructor. A maioria dos desenvolvedores chama o construtor sem parâmetros, que usa o relógio do sistema.Most developers call the parameterless constructor, which uses the system clock. O exemplo a seguir usa essa abordagem para instanciar duas Random instâncias.The following example uses this approach to instantiate two Random instances. Cada instância exibe uma série de 10 inteiros aleatórios.Each instance displays a series of 10 random integers.

using namespace System;
using namespace System::Threading;

void main()
{
Console::WriteLine("Instantiating two random number generators...");
Random^ rnd1 = gcnew Random();
Thread::Sleep(2000);
Random^ rnd2 = gcnew Random();

Console::WriteLine("\nThe first random number generator:");
for (int ctr = 1; ctr <= 10; ctr++)
Console::WriteLine("   {0}", rnd1->Next());

Console::WriteLine("\nThe second random number generator:");
for (int ctr = 1; ctr <= 10; ctr++)
Console::WriteLine("   {0}", rnd2->Next());
}
// The example displays output like the following:
//       Instantiating two random number generators...
//
//       The first random number generator:
//          643164361
//          1606571630
//          1725607587
//          2138048432
//          496874898
//          1969147632
//          2034533749
//          1840964542
//          412380298
//          47518930
//
//       The second random number generator:
//          1251659083
//          1514185439
//          1465798544
//          517841554
//          1821920222
//          195154223
//          1538948391
//          1548375095
//          546062716
//          897797880
using System;
using System.Threading;

public class Example
{
public static void Main()
{
Console.WriteLine("Instantiating two random number generators...");
Random rnd1 = new Random();
Thread.Sleep(2000);
Random rnd2 = new Random();

Console.WriteLine("\nThe first random number generator:");
for (int ctr = 1; ctr <= 10; ctr++)
Console.WriteLine("   {0}", rnd1.Next());

Console.WriteLine("\nThe second random number generator:");
for (int ctr = 1; ctr <= 10; ctr++)
Console.WriteLine("   {0}", rnd2.Next());
}
}
// The example displays output like the following:
//       Instantiating two random number generators...
//
//       The first random number generator:
//          643164361
//          1606571630
//          1725607587
//          2138048432
//          496874898
//          1969147632
//          2034533749
//          1840964542
//          412380298
//          47518930
//
//       The second random number generator:
//          1251659083
//          1514185439
//          1465798544
//          517841554
//          1821920222
//          195154223
//          1538948391
//          1548375095
//          546062716
//          897797880
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
' The example displays output like the following:
'       Instantiating two random number generators...
'
'       The first random number generator:
'          643164361
'          1606571630
'          1725607587
'          2138048432
'          496874898
'          1969147632
'          2034533749
'          1840964542
'          412380298
'          47518930
'
'       The second random number generator:
'          1251659083
'          1514185439
'          1465798544
'          517841554
'          1821920222
'          195154223
'          1538948391
'          1548375095
'          546062716
'          897797880

No entanto, devido à sua resolução finita, o relógio do sistema não detecta diferenças de tempo que são menores que aproximadamente 15 milissegundos.However, because of its finite resolution, the system clock doesn't detect time differences that are less than approximately 15 milliseconds. Portanto, se o seu código chamar a Random() sobrecarga no .NET Framework para instanciar dois Random objetos sucessivamente, você poderá, inadvertidamente, fornecer os objetos com valores de semente idênticos.Therefore, if your code calls the Random() overload on the .NET Framework to instantiate two Random objects in succession, you might inadvertently be providing the objects with identical seed values. (A Random classe no .NET Core não tem essa limitação.) Para ver isso no exemplo anterior, comente a chamada do Thread.Sleep método e compile e execute o exemplo novamente.(The Random class in .NET Core does not have this limitation.) To see this in the previous example, comment out the Thread.Sleep method call, and compile and run the example again.

Para evitar que isso aconteça, recomendamos que você crie uma instância de um único Random objeto em vez de vários.To prevent this from happening, we recommend that you instantiate a single Random object rather than multiple ones. No entanto, como Random não é thread-safe, você deve usar algum dispositivo de sincronização se acessar uma Random instância de vários threads; para obter mais informações, consulte a classe aleatória e a segurança do thread anteriormente neste tópico.However, since Random isn't thread safe, you must use some synchronization device if you access a Random instance from multiple threads; for more information, see The Random class and thread safety earlier in this topic. Como alternativa, você pode usar um mecanismo de atraso, como o Sleep método usado no exemplo anterior, para garantir que as instanciações ocorram mais de 15 milissegundos de distância.Alternately, you can use a delay mechanism, such as the Sleep method used in the previous example, to ensure that the instantiations occur more than 15 millisecond apart.

#### Recuperar inteiros em um intervalo especificadoRetrieve integers in a specified range

Você pode recuperar inteiros em um intervalo especificado chamando o Next(Int32, Int32) método, que permite especificar os limites inferior e superior dos números que você deseja que o gerador de número aleatório retorne.You can retrieve integers in a specified range by calling the Next(Int32, Int32) method, which lets you specify both the lower and the upper bound of the numbers you'd like the random number generator to return. O limite superior é um valor exclusivo, e não inclusivo.The upper bound is an exclusive, not an inclusive, value. Ou seja, ele não está incluído no intervalo de valores retornados pelo método.That is, it isn't included in the range of values returned by the method. O exemplo a seguir usa esse método para gerar inteiros aleatórios entre-10 e 10.The following example uses this method to generate random integers between -10 and 10. Observe que ele especifica 11, que é um maior que o valor desejado, como o valor do maxValue argumento na chamada do método.Note that it specifies 11, which is one greater than the desired value, as the value of the maxValue argument in the method call.

using namespace System;

void main()
{
Random^ rnd = gcnew Random();
for (int ctr = 1; ctr <= 15; ctr++) {
Console::Write("{0,3}    ", rnd->Next(-10, 11));
if(ctr % 5 == 0) Console::WriteLine();
}
}
// The example displays output like the following:
//        -2     -5     -1     -2     10
//        -3      6     -4     -8      3
//        -7     10      5     -2      4
Random rnd = new Random();
for (int ctr = 1; ctr <= 15; ctr++) {
Console.Write("{0,3}    ", rnd.Next(-10, 11));
if(ctr % 5 == 0) Console.WriteLine();
}

// The example displays output like the following:
//        -2     -5     -1     -2     10
//        -3      6     -4     -8      3
//        -7     10      5     -2      4
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
' The example displays output like the following:
'        -2     -5     -1     -2     10
'        -3      6     -4     -8      3
'        -7     10      5     -2      4

#### Recuperar números inteiros com um número especificado de dígitosRetrieve integers with a specified number of digits

Você pode chamar o Next(Int32, Int32) método para recuperar números com um número especificado de dígitos.You can call the Next(Int32, Int32) method to retrieve numbers with a specified number of digits. Por exemplo, para recuperar números com quatro dígitos (ou seja, números que variam de 1000 a 9999), você chama o Next(Int32, Int32) método com um minValue valor de 1000 e um maxValue valor de 10000, como mostra o exemplo a seguir.For example, to retrieve numbers with four digits (that is, numbers that range from 1000 to 9999), you call the Next(Int32, Int32) method with a minValue value of 1000 and a maxValue value of 10000, as the following example shows.

using namespace System;

void main()
{
Random^ rnd = gcnew Random();
for (int ctr = 1; ctr <= 50; ctr++) {
Console::Write("{0,3}   ", rnd->Next(1000, 10000));
if(ctr % 10 == 0) Console::WriteLine();
}
}
// The example displays output like the following:
//    9570    8979    5770    1606    3818    4735    8495    7196    7070    2313
//    5279    6577    5104    5734    4227    3373    7376    6007    8193    5540
//    7558    3934    3819    7392    1113    7191    6947    4963    9179    7907
//    3391    6667    7269    1838    7317    1981    5154    7377    3297    5320
//    9869    8694    2684    4949    2999    3019    2357    5211    9604    2593
Random rnd = new Random();
for (int ctr = 1; ctr <= 50; ctr++) {
Console.Write("{0,3}    ", rnd.Next(1000, 10000));
if(ctr % 10 == 0) Console.WriteLine();
}

// The example displays output like the following:
//    9570    8979    5770    1606    3818    4735    8495    7196    7070    2313
//    5279    6577    5104    5734    4227    3373    7376    6007    8193    5540
//    7558    3934    3819    7392    1113    7191    6947    4963    9179    7907
//    3391    6667    7269    1838    7317    1981    5154    7377    3297    5320
//    9869    8694    2684    4949    2999    3019    2357    5211    9604    2593
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
' The example displays output like the following:
'    9570    8979    5770    1606    3818    4735    8495    7196    7070    2313
'    5279    6577    5104    5734    4227    3373    7376    6007    8193    5540
'    7558    3934    3819    7392    1113    7191    6947    4963    9179    7907
'    3391    6667    7269    1838    7317    1981    5154    7377    3297    5320
'    9869    8694    2684    4949    2999    3019    2357    5211    9604    2593

#### Recuperar valores de ponto flutuante em um intervalo especificadoRetrieve floating-point values in a specified range

O NextDouble método retorna valores de ponto flutuante aleatórios que variam de 0 a menos de 1.The NextDouble method returns random floating-point values that range from 0 to less than 1. No entanto, muitas vezes você desejará gerar valores aleatórios em algum outro intervalo.However, you'll often want to generate random values in some other range.

Se o intervalo entre os valores mínimo e máximo desejado for 1, você poderá adicionar a diferença entre o intervalo inicial desejado e 0 ao número retornado pelo NextDouble método.If the interval between the minimum and maximum desired values is 1, you can add the difference between the desired starting interval and 0 to the number returned by the NextDouble method. O exemplo a seguir faz isso para gerar 10 números aleatórios entre-1 e 0.The following example does this to generate 10 random numbers between -1 and 0.

using namespace System;

void main()
{
Random^ rnd = gcnew Random();
for (int ctr = 1; ctr <= 10; ctr++)
Console::WriteLine(rnd->NextDouble() - 1);
}
// The example displays output like the following:
//       -0.930412760437658
//       -0.164699016215605
//       -0.9851692803135
//       -0.43468508843085
//       -0.177202483255976
//       -0.776813320245972
//       -0.0713201854710096
//       -0.0912875561468711
//       -0.540621722368813
//       -0.232211863730201
Random rnd = new Random();
for (int ctr = 1; ctr <= 10; ctr++)
Console.WriteLine(rnd.NextDouble() - 1);

// The example displays output like the following:
//       -0.930412760437658
//       -0.164699016215605
//       -0.9851692803135
//       -0.43468508843085
//       -0.177202483255976
//       -0.776813320245972
//       -0.0713201854710096
//       -0.0912875561468711
//       -0.540621722368813
//       -0.232211863730201
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
' The example displays output like the following:
'       -0.930412760437658
'       -0.164699016215605
'       -0.9851692803135
'       -0.43468508843085
'       -0.177202483255976
'       -0.776813320245972
'       -0.0713201854710096
'       -0.0912875561468711
'       -0.540621722368813
'       -0.232211863730201

Para gerar números aleatórios de ponto flutuante cujo limite inferior é 0, mas o limite superior é maior que 1 (ou, no caso de números negativos, cujo limite inferior é menor que-1 e o limite superior é 0), multiplique o número aleatório pelo limite diferente de zero.To generate random floating-point numbers whose lower bound is 0 but upper bound is greater than 1 (or, in the case of negative numbers, whose lower bound is less than -1 and upper bound is 0), multiply the random number by the non-zero bound. O exemplo a seguir faz isso para gerar 20 milhões números de ponto flutuante aleatórios que variam de 0 a Int64.MaxValue .The following example does this to generate 20 million random floating-point numbers that range from 0 to Int64.MaxValue. Também exibe a distribuição dos valores aleatórios gerados pelo método.In also displays the distribution of the random values generated by the method.

using namespace System;

void main()
{
const Int64 ONE_TENTH = 922337203685477581;
Random^ rnd = gcnew Random();
double number;
array<int>^ count = gcnew array<int>(10);

// Generate 20 million integer values between.
for (int ctr = 1; ctr <= 20000000; ctr++) {
number = rnd->NextDouble() * Int64::MaxValue;
// Categorize random numbers into 10 groups.
int value = (int) (number / ONE_TENTH);
count[value]++;
}

// Display breakdown by range.
Console::WriteLine("{0,28} {1,32}   {2,7}\n", "Range", "Count", "Pct.");
for (int ctr = 0; ctr <= 9; ctr++)
Console::WriteLine("{0,25:N0}-{1,25:N0}  {2,8:N0}   {3,7:P2}", ctr * ONE_TENTH,
ctr < 9 ? ctr * ONE_TENTH + ONE_TENTH - 1 : Int64::MaxValue,
count[ctr], count[ctr]/20000000.0);
}
// The example displays output like the following:
//                           Range                            Count      Pct.
//
//                            0-  922,337,203,685,477,580  1,996,148    9.98 %
//      922,337,203,685,477,581-1,844,674,407,370,955,161  2,000,293   10.00 %
//    1,844,674,407,370,955,162-2,767,011,611,056,432,742  2,000,094   10.00 %
//    2,767,011,611,056,432,743-3,689,348,814,741,910,323  2,000,159   10.00 %
//    3,689,348,814,741,910,324-4,611,686,018,427,387,904  1,999,552   10.00 %
//    4,611,686,018,427,387,905-5,534,023,222,112,865,485  1,998,248    9.99 %
//    5,534,023,222,112,865,486-6,456,360,425,798,343,066  2,000,696   10.00 %
//    6,456,360,425,798,343,067-7,378,697,629,483,820,647  2,001,637   10.01 %
//    7,378,697,629,483,820,648-8,301,034,833,169,298,228  2,002,870   10.01 %
//    8,301,034,833,169,298,229-9,223,372,036,854,775,807  2,000,303   10.00 %
const long ONE_TENTH = 922337203685477581;

Random rnd = new Random();
double number;
int[] count = new int[10];

// Generate 20 million integer values between.
for (int ctr = 1; ctr <= 20000000; ctr++) {
number = rnd.NextDouble() * Int64.MaxValue;
// Categorize random numbers into 10 groups.
count[(int) (number / ONE_TENTH)]++;
}
// Display breakdown by range.
Console.WriteLine("{0,28} {1,32}   {2,7}\n", "Range", "Count", "Pct.");
for (int ctr = 0; ctr <= 9; ctr++)
Console.WriteLine("{0,25:N0}-{1,25:N0}  {2,8:N0}   {3,7:P2}", ctr * ONE_TENTH,
ctr < 9 ? ctr * ONE_TENTH + ONE_TENTH - 1 : Int64.MaxValue,
count[ctr], count[ctr]/20000000.0);

// The example displays output like the following:
//                           Range                            Count      Pct.
//
//                            0-  922,337,203,685,477,580  1,996,148    9.98 %
//      922,337,203,685,477,581-1,844,674,407,370,955,161  2,000,293   10.00 %
//    1,844,674,407,370,955,162-2,767,011,611,056,432,742  2,000,094   10.00 %
//    2,767,011,611,056,432,743-3,689,348,814,741,910,323  2,000,159   10.00 %
//    3,689,348,814,741,910,324-4,611,686,018,427,387,904  1,999,552   10.00 %
//    4,611,686,018,427,387,905-5,534,023,222,112,865,485  1,998,248    9.99 %
//    5,534,023,222,112,865,486-6,456,360,425,798,343,066  2,000,696   10.00 %
//    6,456,360,425,798,343,067-7,378,697,629,483,820,647  2,001,637   10.01 %
//    7,378,697,629,483,820,648-8,301,034,833,169,298,228  2,002,870   10.01 %
//    8,301,034,833,169,298,229-9,223,372,036,854,775,807  2,000,303   10.00 %
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
' The example displays output like the following:
'                           Range                            Count      Pct.
'
'                            0-  922,337,203,685,477,580  1,996,148    9.98 %
'      922,337,203,685,477,581-1,844,674,407,370,955,161  2,000,293   10.00 %
'    1,844,674,407,370,955,162-2,767,011,611,056,432,742  2,000,094   10.00 %
'    2,767,011,611,056,432,743-3,689,348,814,741,910,323  2,000,159   10.00 %
'    3,689,348,814,741,910,324-4,611,686,018,427,387,904  1,999,552   10.00 %
'    4,611,686,018,427,387,905-5,534,023,222,112,865,485  1,998,248    9.99 %
'    5,534,023,222,112,865,486-6,456,360,425,798,343,066  2,000,696   10.00 %
'    6,456,360,425,798,343,067-7,378,697,629,483,820,647  2,001,637   10.01 %
'    7,378,697,629,483,820,648-8,301,034,833,169,298,228  2,002,870   10.01 %
'    8,301,034,833,169,298,229-9,223,372,036,854,775,807  2,000,303   10.00 %

Para gerar números de ponto flutuante aleatório entre dois valores arbitrários, como o Next(Int32, Int32) método faz para inteiros, use a seguinte fórmula:To generate random floating-point numbers between two arbitrary values, like the Next(Int32, Int32) method does for integers, use the following formula:

Random.NextDouble() * (maxValue - minValue) + minValue

O exemplo a seguir gera 1 milhão números aleatórios que variam de 10,0 a 11,0 e exibe sua distribuição.The following example generates 1 million random numbers that range from 10.0 to 11.0, and displays their distribution.

using namespace System;

void main()
{
Random^ rnd = gcnew Random();
int lowerBound = 10;
int upperBound = 11;
array<int>^ range = gcnew array<int>(10);
for (int ctr = 1; ctr <= 1000000; ctr++) {
Double value = rnd->NextDouble() * (upperBound - lowerBound) + lowerBound;
range[(int) Math::Truncate((value - lowerBound) * 10)]++;
}

for (int ctr = 0; ctr <= 9; ctr++) {
Double lowerRange = 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);
}
}
// The example displays output like the following:
//       10.0 to 10.1:   99,929  ( 9.99 %)
//       10.1 to 10.2:  100,189  (10.02 %)
//       10.2 to 10.3:   99,384  ( 9.94 %)
//       10.3 to 10.4:  100,240  (10.02 %)
//       10.4 to 10.5:   99,397  ( 9.94 %)
//       10.5 to 10.6:  100,580  (10.06 %)
//       10.6 to 10.7:  100,293  (10.03 %)
//       10.7 to 10.8:  100,135  (10.01 %)
//       10.8 to 10.9:   99,905  ( 9.99 %)
//       10.9 to 11.0:   99,948  ( 9.99 %)
Random rnd = new Random();
int lowerBound = 10;
int upperBound = 11;
int[] range = new int[10];
for (int ctr = 1; ctr <= 1000000; ctr++) {
Double value = rnd.NextDouble() * (upperBound - lowerBound) + lowerBound;
range[(int) Math.Truncate((value - lowerBound) * 10)]++;
}

for (int ctr = 0; ctr <= 9; ctr++) {
Double lowerRange = 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);
}

// The example displays output like the following:
//       10.0 to 10.1:   99,929  ( 9.99 %)
//       10.1 to 10.2:  100,189  (10.02 %)
//       10.2 to 10.3:   99,384  ( 9.94 %)
//       10.3 to 10.4:  100,240  (10.02 %)
//       10.4 to 10.5:   99,397  ( 9.94 %)
//       10.5 to 10.6:  100,580  (10.06 %)
//       10.6 to 10.7:  100,293  (10.03 %)
//       10.7 to 10.8:  100,135  (10.01 %)
//       10.8 to 10.9:   99,905  ( 9.99 %)
//       10.9 to 11.0:   99,948  ( 9.99 %)
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
' The example displays output like the following:
'       10.0 to 10.1:   99,929  ( 9.99 %)
'       10.1 to 10.2:  100,189  (10.02 %)
'       10.2 to 10.3:   99,384  ( 9.94 %)
'       10.3 to 10.4:  100,240  (10.02 %)
'       10.4 to 10.5:   99,397  ( 9.94 %)
'       10.5 to 10.6:  100,580  (10.06 %)
'       10.6 to 10.7:  100,293  (10.03 %)
'       10.7 to 10.8:  100,135  (10.01 %)
'       10.8 to 10.9:   99,905  ( 9.99 %)
'       10.9 to 11.0:   99,948  ( 9.99 %)

#### Gerar valores Boolianos aleatóriosGenerate random Boolean values

A Random classe não fornece métodos que geram Boolean valores.The Random class doesn't provide methods that generate Boolean values. No entanto, você pode definir sua própria classe ou método para fazer isso.However, you can define your own class or method to do that. O exemplo a seguir define uma classe, BooleanGenerator , com um único método, NextBoolean .The following example defines a class, BooleanGenerator, with a single method, NextBoolean. A BooleanGenerator classe armazena um Random objeto como uma variável privada.The BooleanGenerator class stores a Random object as a private variable. O NextBoolean método chama o Random.Next(Int32, Int32) método e passa o resultado para o Convert.ToBoolean(Int32) método.The NextBoolean method calls the Random.Next(Int32, Int32) method and passes the result to the Convert.ToBoolean(Int32) method. Observe que 2 é usado como o argumento para especificar o limite superior do número aleatório.Note that 2 is used as the argument to specify the upper bound of the random number. Como esse é um valor exclusivo, a chamada do método retorna 0 ou 1.Since this is an exclusive value, the method call returns either 0 or 1.

using namespace System;

public ref class BooleanGenerator
{
private:
Random^ rnd;

public:
BooleanGenerator()
{
rnd = gcnew Random();
}

bool NextBoolean()
{
return Convert::ToBoolean(rnd->Next(0, 2));
}
};

void main()
{
// Instantiate the Boolean generator.
BooleanGenerator^ boolGen = gcnew BooleanGenerator();
int totalTrue = 0, totalFalse = 0;

// Generate 1,0000 random Booleans, and keep a running total.
for (int ctr = 0; ctr < 1000000; ctr++) {
bool value = boolGen->NextBoolean();
if (value)
totalTrue++;
else
totalFalse++;
}
Console::WriteLine("Number of true values:  {0,7:N0} ({1:P3})",
totalTrue,
((double) totalTrue)/(totalTrue + totalFalse));
Console::WriteLine("Number of false values: {0,7:N0} ({1:P3})",
totalFalse,
((double) totalFalse)/(totalTrue + totalFalse));
}

// The example displays output like the following:
//       Number of true values:  500,004 (50.000 %)
//       Number of false values: 499,996 (50.000 %)
using System;

public class Example
{
public static void Main()
{
// Instantiate the Boolean generator.
BooleanGenerator boolGen = new BooleanGenerator();
int totalTrue = 0, totalFalse = 0;

// Generate 1,0000 random Booleans, and keep a running total.
for (int ctr = 0; ctr < 1000000; ctr++) {
bool value = boolGen.NextBoolean();
if (value)
totalTrue++;
else
totalFalse++;
}
Console.WriteLine("Number of true values:  {0,7:N0} ({1:P3})",
totalTrue,
((double) totalTrue)/(totalTrue + totalFalse));
Console.WriteLine("Number of false values: {0,7:N0} ({1:P3})",
totalFalse,
((double) totalFalse)/(totalTrue + totalFalse));
}
}

public class BooleanGenerator
{
Random rnd;

public BooleanGenerator()
{
rnd = new Random();
}

public bool NextBoolean()
{
return Convert.ToBoolean(rnd.Next(0, 2));
}
}
// The example displays output like the following:
//       Number of true values:  500,004 (50.000 %)
//       Number of false values: 499,996 (50.000 %)
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
' The example displays the following output:
'       Number of true values:  500,004 (50.000 %)
'       Number of false values: 499,996 (50.000 %)

Em vez de criar uma classe separada para gerar Boolean valores aleatórios, o exemplo poderia simplesmente ter definido um único método.Instead of creating a separate class to generate random Boolean values, the example could simply have defined a single method. Nesse caso, no entanto, o Random objeto deve ter sido definido como uma variável em nível de classe para evitar a instanciação de uma nova Random instância em cada chamada de método.In that case, however, the Random object should have been defined as a class-level variable to avoid instantiating a new Random instance in each method call. No Visual Basic, a instância aleatória pode ser definida como uma variável estática no NextBoolean método.In Visual Basic, the Random instance can be defined as a Static variable in the NextBoolean method. O exemplo a seguir fornece uma implementação.The following example provides an implementation.

using namespace System;

ref class Example
{
private:
static Random^ rnd = gcnew Random();

public:
static void Execute()
{
int totalTrue = 0, totalFalse = 0;

// Generate 1,0000 random Booleans, and keep a running total.
for (int ctr = 0; ctr < 1000000; ctr++) {
bool value = NextBoolean();
if (value)
totalTrue++;
else
totalFalse++;
}
Console::WriteLine("Number of true values:  {0,7:N0} ({1:P3})",
totalTrue,
((double) totalTrue)/(totalTrue + totalFalse));
Console::WriteLine("Number of false values: {0,7:N0} ({1:P3})",
totalFalse,
((double) totalFalse)/(totalTrue + totalFalse));
}

static bool NextBoolean()
{
return Convert::ToBoolean(rnd->Next(0, 2));
}
};

void main()
{
Example::Execute();
}
// The example displays output like the following:
//       Number of true values:  499,777 (49.978 %)
//       Number of false values: 500,223 (50.022 %)
Random rnd = new Random();

int totalTrue = 0, totalFalse = 0;

// Generate 1,000,000 random Booleans, and keep a running total.
for (int ctr = 0; ctr < 1000000; ctr++) {
bool value = NextBoolean();
if (value)
totalTrue++;
else
totalFalse++;
}
Console.WriteLine("Number of true values:  {0,7:N0} ({1:P3})",
totalTrue,
((double) totalTrue)/(totalTrue + totalFalse));
Console.WriteLine("Number of false values: {0,7:N0} ({1:P3})",
totalFalse,
((double) totalFalse)/(totalTrue + totalFalse));

bool NextBoolean()
{
return Convert.ToBoolean(rnd.Next(0, 2));
}

// The example displays output like the following:
//       Number of true values:  499,777 (49.978 %)
//       Number of false values: 500,223 (50.022 %)
Module Example
Public Sub Main()
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 = 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

Public Function NextBoolean() As Boolean
Static rnd As New Random()
Return Convert.ToBoolean(rnd.Next(0, 2))
End Function
End Module
' The example displays the following output:
'       Number of true values:  499,777 (49.978 %)
'       Number of false values: 500,223 (50.022 %)

#### Gerar inteiros aleatórios de 64 bitsGenerate random 64-bit integers

As sobrecargas do Next método retornam inteiros de 32 bits.The overloads of the Next method return 32-bit integers. No entanto, em alguns casos, talvez você queira trabalhar com inteiros de 64 bits.However, in some cases, you might want to work with 64-bit integers. Você pode fazer isso da seguinte maneira:You can do this as follows:

1. Chame o NextDouble método para recuperar um valor de ponto flutuante de precisão dupla.Call the NextDouble method to retrieve a double-precision floating point value.

2. Multiplique esse valor por Int64.MaxValue .Multiply that value by Int64.MaxValue.

O exemplo a seguir usa essa técnica para gerar 20 milhões inteiros longos aleatórios e os categoriza em 10 grupos iguais.The following example uses this technique to generate 20 million random long integers and categorizes them in 10 equal groups. Em seguida, ele avalia a distribuição dos números aleatórios contando o número em cada grupo de 0 a Int64.MaxValue .It then evaluates the distribution of the random numbers by counting the number in each group from 0 to Int64.MaxValue. Como a saída do exemplo mostra, os números são distribuídos mais ou menos igualmente por meio do intervalo de um inteiro longo.As the output from the example shows, the numbers are distributed more or less equally through the range of a long integer.

using namespace System;

void main()
{
const Int64 ONE_TENTH = 922337203685477581;

Random^ rnd = gcnew Random();
Int64 number;
array<int>^ count = gcnew array<int>(10);

// Generate 20 million long integers.
for (int ctr = 1; ctr <= 20000000; ctr++) {
number = (Int64) (rnd->NextDouble() * Int64::MaxValue);
// Categorize random numbers.
count[(int) (number / ONE_TENTH)]++;
}
// Display breakdown by range.
Console::WriteLine("{0,28} {1,32}   {2,7}\n", "Range", "Count", "Pct.");
for (int ctr = 0; ctr <= 9; ctr++)
Console::WriteLine("{0,25:N0}-{1,25:N0}  {2,8:N0}   {3,7:P2}", ctr * ONE_TENTH,
ctr < 9 ? ctr * ONE_TENTH + ONE_TENTH - 1 : Int64::MaxValue,
count[ctr], count[ctr]/20000000.0);
}
// The example displays output like the following:
//                           Range                            Count      Pct.
//
//                            0-  922,337,203,685,477,580  1,996,148    9.98 %
//      922,337,203,685,477,581-1,844,674,407,370,955,161  2,000,293   10.00 %
//    1,844,674,407,370,955,162-2,767,011,611,056,432,742  2,000,094   10.00 %
//    2,767,011,611,056,432,743-3,689,348,814,741,910,323  2,000,159   10.00 %
//    3,689,348,814,741,910,324-4,611,686,018,427,387,904  1,999,552   10.00 %
//    4,611,686,018,427,387,905-5,534,023,222,112,865,485  1,998,248    9.99 %
//    5,534,023,222,112,865,486-6,456,360,425,798,343,066  2,000,696   10.00 %
//    6,456,360,425,798,343,067-7,378,697,629,483,820,647  2,001,637   10.01 %
//    7,378,697,629,483,820,648-8,301,034,833,169,298,228  2,002,870   10.01 %
//    8,301,034,833,169,298,229-9,223,372,036,854,775,807  2,000,303   10.00 %
const long ONE_TENTH = 922337203685477581;

Random rnd = new Random();
long number;
int[] count = new int[10];

// Generate 20 million long integers.
for (int ctr = 1; ctr <= 20000000; ctr++) {
number = (long) (rnd.NextDouble() * Int64.MaxValue);
// Categorize random numbers.
count[(int) (number / ONE_TENTH)]++;
}
// Display breakdown by range.
Console.WriteLine("{0,28} {1,32}   {2,7}\n", "Range", "Count", "Pct.");
for (int ctr = 0; ctr <= 9; ctr++)
Console.WriteLine("{0,25:N0}-{1,25:N0}  {2,8:N0}   {3,7:P2}", ctr * ONE_TENTH,
ctr < 9 ? ctr * ONE_TENTH + ONE_TENTH - 1 : Int64.MaxValue,
count[ctr], count[ctr]/20000000.0);

// The example displays output like the following:
//                           Range                            Count      Pct.
//
//                            0-  922,337,203,685,477,580  1,996,148    9.98 %
//      922,337,203,685,477,581-1,844,674,407,370,955,161  2,000,293   10.00 %
//    1,844,674,407,370,955,162-2,767,011,611,056,432,742  2,000,094   10.00 %
//    2,767,011,611,056,432,743-3,689,348,814,741,910,323  2,000,159   10.00 %
//    3,689,348,814,741,910,324-4,611,686,018,427,387,904  1,999,552   10.00 %
//    4,611,686,018,427,387,905-5,534,023,222,112,865,485  1,998,248    9.99 %
//    5,534,023,222,112,865,486-6,456,360,425,798,343,066  2,000,696   10.00 %
//    6,456,360,425,798,343,067-7,378,697,629,483,820,647  2,001,637   10.01 %
//    7,378,697,629,483,820,648-8,301,034,833,169,298,228  2,002,870   10.01 %
//    8,301,034,833,169,298,229-9,223,372,036,854,775,807  2,000,303   10.00 %
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 long integers.
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
' The example displays output like the following:
'                           Range                            Count      Pct.
'
'                            0-  922,337,203,685,477,580  1,996,148    9.98 %
'      922,337,203,685,477,581-1,844,674,407,370,955,161  2,000,293   10.00 %
'    1,844,674,407,370,955,162-2,767,011,611,056,432,742  2,000,094   10.00 %
'    2,767,011,611,056,432,743-3,689,348,814,741,910,323  2,000,159   10.00 %
'    3,689,348,814,741,910,324-4,611,686,018,427,387,904  1,999,552   10.00 %
'    4,611,686,018,427,387,905-5,534,023,222,112,865,485  1,998,248    9.99 %
'    5,534,023,222,112,865,486-6,456,360,425,798,343,066  2,000,696   10.00 %
'    6,456,360,425,798,343,067-7,378,697,629,483,820,647  2,001,637   10.01 %
'    7,378,697,629,483,820,648-8,301,034,833,169,298,228  2,002,870   10.01 %
'    8,301,034,833,169,298,229-9,223,372,036,854,775,807  2,000,303   10.00 %

Uma técnica alternativa que usa a manipulação de bits não gera números verdadeiramente aleatórios.An alternative technique that uses bit manipulation does not generate truly random numbers. Essa técnica chama Next() para gerar dois inteiros, com SHIFT esquerda um de 32 bits e o ORS juntos.This technique calls Next() to generate two integers, left-shifts one by 32 bits, and ORs them together. Essa técnica tem duas limitações:This technique has two limitations:

1. Como o bit 31 é o bit de sinal, o valor no bit 31 do inteiro longo resultante é sempre 0.Because bit 31 is the sign bit, the value in bit 31 of the resulting long integer is always 0. Isso pode ser resolvido gerando um valor aleatório 0 ou 1, com deslocamento à esquerda de 31 bits e ORing-lo com o inteiro longo aleatório original.This can be addressed by generating a random 0 or 1, left-shifting it 31 bits, and ORing it with the original random long integer.

2. Mais seriamente, como a probabilidade de que o valor retornado Next() seja 0, haverá alguns números aleatórios no intervalo 0x0-0x00000000FFFFFFFF.More seriously, because the probability that the value returned by Next() will be 0, there will be few if any random numbers in the range 0x0-0x00000000FFFFFFFF.

#### Recuperar bytes em um intervalo especificadoRetrieve bytes in a specified range

As sobrecargas do Next método permitem que você especifique o intervalo de números aleatórios, mas o NextBytes método não faz isso.The overloads of the Next method allow you to specify the range of random numbers, but the NextBytes method does not. O exemplo a seguir implementa um NextBytes método que permite especificar o intervalo dos bytes retornados.The following example implements a NextBytes method that lets you specify the range of the returned bytes. Ele define uma Random2 classe que deriva de Random e sobrecarrega seu NextBytes método.It defines a Random2 class that derives from Random and overloads its NextBytes method.

using namespace System;

ref class Random2 : Random
{
public:
Random2()
{}

Random2(int seed) : Random(seed)
{}

void NextBytes(array<Byte>^ bytes, Byte minValue, Byte maxValue)
{
for (int ctr = bytes->GetLowerBound(0); ctr <= bytes->GetUpperBound(0); ctr++)
bytes[ctr] = (Byte) Next(minValue, maxValue);
}
};

void main()
{
Random2^ rnd = gcnew Random2();
array<Byte>^ bytes = gcnew array<Byte>(10000);
array<int>^ total = gcnew array<int>(101);
rnd->NextBytes(bytes, 0, 101);

// Calculate how many of each value we have.
for each (Byte value in bytes)
total[value]++;

// Display the results.
for (int ctr = 0; ctr < total->Length; ctr++) {
Console::Write("{0,3}: {1,-3}   ", ctr, total[ctr]);
if ((ctr + 1) % 5 == 0) Console::WriteLine();
}
}
// The example displays output like the following:
//         0: 115     1: 119     2: 92      3: 98      4: 92
//         5: 102     6: 103     7: 84      8: 93      9: 116
//        10: 91     11: 98     12: 106    13: 91     14: 92
//        15: 101    16: 100    17: 96     18: 97     19: 100
//        20: 101    21: 106    22: 112    23: 82     24: 85
//        25: 102    26: 107    27: 98     28: 106    29: 102
//        30: 109    31: 108    32: 94     33: 101    34: 107
//        35: 101    36: 86     37: 100    38: 101    39: 102
//        40: 113    41: 95     42: 96     43: 89     44: 99
//        45: 81     46: 89     47: 105    48: 100    49: 85
//        50: 103    51: 103    52: 93     53: 89     54: 91
//        55: 97     56: 105    57: 97     58: 110    59: 86
//        60: 116    61: 94     62: 117    63: 98     64: 110
//        65: 93     66: 102    67: 100    68: 105    69: 83
//        70: 81     71: 97     72: 85     73: 70     74: 98
//        75: 100    76: 110    77: 114    78: 83     79: 90
//        80: 96     81: 112    82: 102    83: 102    84: 99
//        85: 81     86: 100    87: 93     88: 99     89: 118
//        90: 95     91: 124    92: 108    93: 96     94: 104
//        95: 106    96: 99     97: 99     98: 92     99: 99
//       100: 108
using System;

public class Example
{
public static void Main()
{
Random2 rnd = new Random2();
Byte[] bytes = new Byte[10000];
int[] total = new int[101];
rnd.NextBytes(bytes, 0, 101);

// Calculate how many of each value we have.
foreach (var value in bytes)
total[value]++;

// Display the results.
for (int ctr = 0; ctr < total.Length; ctr++) {
Console.Write("{0,3}: {1,-3}   ", ctr, total[ctr]);
if ((ctr + 1) % 5 == 0) Console.WriteLine();
}
}
}

public class Random2 : Random
{
public Random2() : base()
{}

public Random2(int seed) : base(seed)
{}

public void NextBytes(byte[] bytes, byte minValue, byte maxValue)
{
for (int ctr = bytes.GetLowerBound(0); ctr <= bytes.GetUpperBound(0); ctr++)
bytes[ctr] = (byte) Next(minValue, maxValue);
}
}
// The example displays output like the following:
//         0: 115     1: 119     2: 92      3: 98      4: 92
//         5: 102     6: 103     7: 84      8: 93      9: 116
//        10: 91     11: 98     12: 106    13: 91     14: 92
//        15: 101    16: 100    17: 96     18: 97     19: 100
//        20: 101    21: 106    22: 112    23: 82     24: 85
//        25: 102    26: 107    27: 98     28: 106    29: 102
//        30: 109    31: 108    32: 94     33: 101    34: 107
//        35: 101    36: 86     37: 100    38: 101    39: 102
//        40: 113    41: 95     42: 96     43: 89     44: 99
//        45: 81     46: 89     47: 105    48: 100    49: 85
//        50: 103    51: 103    52: 93     53: 89     54: 91
//        55: 97     56: 105    57: 97     58: 110    59: 86
//        60: 116    61: 94     62: 117    63: 98     64: 110
//        65: 93     66: 102    67: 100    68: 105    69: 83
//        70: 81     71: 97     72: 85     73: 70     74: 98
//        75: 100    76: 110    77: 114    78: 83     79: 90
//        80: 96     81: 112    82: 102    83: 102    84: 99
//        85: 81     86: 100    87: 93     88: 99     89: 118
//        90: 95     91: 124    92: 108    93: 96     94: 104
//        95: 106    96: 99     97: 99     98: 92     99: 99
//       100: 108
Module Example
Public Sub Main()
Dim rnd As New Random2()
Dim bytes(9999) As Byte
Dim total(100) As Integer
rnd.NextBytes(bytes, 0, 101)

' Calculate how many of each value we have.
For Each value In bytes
total(value) += 1
Next

' Display the results.
For ctr As Integer = 0 To total.Length - 1
Console.Write("{0,3}: {1,-3}   ", ctr, total(ctr))
If (ctr + 1) Mod 5 = 0 Then Console.WriteLine()
Next
End Sub
End Module

Public Class Random2 : Inherits Random
Public Sub New()
MyBase.New()
End Sub

Public Sub New(seed As Integer)
MyBase.New(seed)
End Sub

Public Overloads Sub NextBytes(bytes() As Byte,
minValue As Byte, maxValue As Byte)
For ctr As Integer = bytes.GetLowerbound(0) To bytes.GetUpperBound(0)
bytes(ctr) = CByte(MyBase.Next(minValue, maxValue))
Next
End Sub
End Class
' The example displays output like the following:
'         0: 115     1: 119     2: 92      3: 98      4: 92
'         5: 102     6: 103     7: 84      8: 93      9: 116
'        10: 91     11: 98     12: 106    13: 91     14: 92
'        15: 101    16: 100    17: 96     18: 97     19: 100
'        20: 101    21: 106    22: 112    23: 82     24: 85
'        25: 102    26: 107    27: 98     28: 106    29: 102
'        30: 109    31: 108    32: 94     33: 101    34: 107
'        35: 101    36: 86     37: 100    38: 101    39: 102
'        40: 113    41: 95     42: 96     43: 89     44: 99
'        45: 81     46: 89     47: 105    48: 100    49: 85
'        50: 103    51: 103    52: 93     53: 89     54: 91
'        55: 97     56: 105    57: 97     58: 110    59: 86
'        60: 116    61: 94     62: 117    63: 98     64: 110
'        65: 93     66: 102    67: 100    68: 105    69: 83
'        70: 81     71: 97     72: 85     73: 70     74: 98
'        75: 100    76: 110    77: 114    78: 83     79: 90
'        80: 96     81: 112    82: 102    83: 102    84: 99
'        85: 81     86: 100    87: 93     88: 99     89: 118
'        90: 95     91: 124    92: 108    93: 96     94: 104
'        95: 106    96: 99     97: 99     98: 92     99: 99
'       100: 108

O NextBytes(Byte[], Byte, Byte) método encapsula uma chamada para o Next(Int32, Int32) método e especifica o valor mínimo e um maior que o valor máximo (nesse caso, 0 e 101) que desejamos retornar na matriz de bytes.The NextBytes(Byte[], Byte, Byte) method wraps a call to the Next(Int32, Int32) method and specifies the minimum value and one greater than the maximum value (in this case, 0 and 101) that we want returned in the byte array. Como temos certeza de que os valores inteiros retornados pelo Next método estão dentro do intervalo do tipo de Byte dados, podemos convertê-los com segurança (em C#) ou convertá-los (em Visual Basic) de inteiros para bytes.Because we are sure that the integer values returned by the Next method are within the range of the Byte data type, we can safely cast them (in C#) or convert them (in Visual Basic) from integers to bytes.

#### Recuperar um elemento de uma matriz ou coleção aleatoriamenteRetrieve an element from an array or collection at random

Os números aleatórios geralmente servem como índices para recuperar valores de matrizes ou coleções.Random numbers often serve as indexes to retrieve values from arrays or collections. Para recuperar um valor de índice aleatório, você pode chamar o Next(Int32, Int32) método e usar o limite inferior da matriz como o valor de seu minValue argumento e um maior que o limite superior da matriz como o valor de seu maxValue argumento.To retrieve a random index value, you can call the Next(Int32, Int32) method, and use the lower bound of the array as the value of its minValue argument and one greater than the upper bound of the array as the value of its maxValue argument. Para uma matriz baseada em zero, isso é equivalente à sua Length propriedade, ou um maior que o valor retornado pelo Array.GetUpperBound método.For a zero-based array, this is equivalent to its Length property, or one greater than the value returned by the Array.GetUpperBound method. O exemplo a seguir recupera aleatoriamente o nome de uma cidade no Estados Unidos de uma matriz de cidades.The following example randomly retrieves the name of a city in the United States from an array of cities.

using namespace System;

void main()
{
array<String^>^ cities = { "Atlanta", "Boston", "Chicago", "Detroit",
"Fort Wayne", "Greensboro", "Honolulu", "Indianapolis",
"Jersey City", "Kansas City", "Los Angeles",
"Milwaukee", "New York", "Omaha", "Philadelphia",
"Raleigh", "San Francisco", "Tulsa", "Washington" };
Random^ rnd = gcnew Random();
int index = rnd->Next(0, cities->Length);
Console::WriteLine("Today's city of the day: {0}",
cities[index]);
}
// The example displays output like the following:
//   Today's city of the day: Honolulu
String[] cities = { "Atlanta", "Boston", "Chicago", "Detroit",
"Fort Wayne", "Greensboro", "Honolulu", "Indianapolis",
"Jersey City", "Kansas City", "Los Angeles",
"Milwaukee", "New York", "Omaha", "Philadelphia",
"Raleigh", "San Francisco", "Tulsa", "Washington" };
Random rnd = new Random();
int index = rnd.Next(0, cities.Length);
Console.WriteLine("Today's city of the day: {0}",
cities[index]);

// The example displays output like the following:
//   Today's city of the day: Honolulu
Module Example
Public Sub Main()
Dim cities() As String = { "Atlanta", "Boston", "Chicago", "Detroit",
"Fort Wayne", "Greensboro", "Honolulu", "Indianapolis",
"Jersey City", "Kansas City", "Los Angeles",
"Milwaukee", "New York", "Omaha", "Philadelphia",
"Raleigh", "San Francisco", "Tulsa", "Washington" }
Dim rnd As New Random()
Dim index As Integer = rnd.Next(0, cities.Length)
Console.WriteLine("Today's city of the day: {0}",
cities(index))
End Sub
End Module
' The example displays output like the following:
'   Today's city of the day: Honolulu

#### Recuperar um elemento exclusivo de uma matriz ou coleçãoRetrieve a unique element from an array or collection

Um gerador de números aleatórios sempre pode retornar valores duplicados.A random number generator can always return duplicate values. Como o intervalo de números se torna menor ou o número de valores gerados se torna maior, a probabilidade de duplicatas aumenta.As the range of numbers becomes smaller or the number of values generated becomes larger, the probability of duplicates grows. Se os valores aleatórios precisarem ser exclusivos, mais números serão gerados para compensar as duplicatas, resultando em um desempenho cada vez mais baixo.If random values must be unique, more numbers are generated to compensate for duplicates, resulting in increasingly poor performance.

Há várias técnicas para lidar com esse cenário.There are a number of techniques to handle this scenario. Uma solução comum é criar uma matriz ou coleção que contenha os valores a serem recuperados e uma matriz paralela que contenha números de ponto flutuante aleatórios.One common solution is to create an array or collection that contains the values to be retrieved, and a parallel array that contains random floating-point numbers. A segunda matriz é preenchida com números aleatórios no momento em que a primeira matriz é criada e o Array.Sort(Array, Array) método é usado para classificar a primeira matriz usando os valores na matriz paralela.The second array is populated with random numbers at the time the first array is created, and the Array.Sort(Array, Array) method is used to sort the first array by using the values in the parallel array.

Por exemplo, se você estiver desenvolvendo um jogo paciência, você deseja garantir que cada cartão seja usado apenas uma vez.For example, if you're developing a Solitaire game, you want to ensure that each card is used only once. Em vez de gerar números aleatórios para recuperar um cartão e controlar se esse cartão já foi tratado, você pode criar uma matriz paralela de números aleatórios que podem ser usados para classificar o baralho.Instead of generating random numbers to retrieve a card and tracking whether that card has already been dealt, you can create a parallel array of random numbers that can be used to sort the deck. Depois que o baralho é classificado, seu aplicativo pode manter um ponteiro para indicar o índice do próximo cartão no baralho.Once the deck is sorted, your app can maintain a pointer to indicate the index of the next card on the deck.

O exemplo a seguir ilustra esta abordagem.The following example illustrates this approach. Ele define uma Card classe que representa um cartão de baralho e uma Dealer classe que lida com um baralho de cartões em ordem aleatória.It defines a Card class that represents a playing card and a Dealer class that deals a deck of shuffled cards. O Dealer Construtor de classe popula duas matrizes: uma deck matriz que tem o escopo de classe e que representa todas as cartas no baralho; e uma order matriz local que tem o mesmo número de elementos que a deck matriz e é preenchida com valores gerados aleatoriamente Double .The Dealer class constructor populates two arrays: a deck array that has class scope and that represents all the cards in the deck; and a local order array that has the same number of elements as the deck array and is populated with randomly generated Double values. O Array.Sort(Array, Array) método é chamado para classificar a deck matriz com base nos valores na order matriz.The Array.Sort(Array, Array) method is then called to sort the deck array based on the values in the order array.

using namespace System;

public enum class Suit { Hearts, Diamonds, Spades, Clubs };

public enum class FaceValue  { Ace = 1, Two, Three, Four, Five, Six,
Seven, Eight, Nine, Ten, Jack, Queen,
King };

// A class that represents an individual card in a playing deck.
ref class Card
{
public:
Suit Suit;
FaceValue FaceValue;

String^ ToString() override
{
return String::Format("{0:F} of {1:F}", this->FaceValue, this->Suit);
}
};

ref class Dealer
{
private:
Random^ rnd;
// A deck of cards, without Jokers.
array<Card^>^ deck = gcnew array<Card^>(52);
// Parallel array for sorting cards.
array<Double>^ order = gcnew array<Double>(52);
// A pointer to the next card to deal.
int ptr = 0;
// A flag to indicate the deck is used.
bool mustReshuffle = false;

public:
Dealer()
{
rnd = gcnew Random();
// Initialize the deck.
int deckCtr = 0;
for each (auto suit in Enum::GetValues(Suit::typeid)) {
for each (FaceValue faceValue in Enum::GetValues(FaceValue::typeid)) {
Card^ card = gcnew Card();
card->Suit = (Suit) suit;
card->FaceValue = (FaceValue) faceValue;
deck[deckCtr] = card;
deckCtr++;
}
}

for (int ctr = 0; ctr < order->Length; ctr++)
order[ctr] = rnd->NextDouble();

Array::Sort(order, deck);
}

array<Card^>^ Deal(int numberToDeal)
{
if (mustReshuffle) {
Console::WriteLine("There are no cards left in the deck");
return nullptr;
}

array<Card^>^ cardsDealt = gcnew array<Card^>(numberToDeal);
for (int ctr = 0; ctr < numberToDeal; ctr++) {
cardsDealt[ctr] = deck[ptr];
ptr++;
if (ptr == deck->Length)
mustReshuffle = true;

if (mustReshuffle & ctr < numberToDeal - 1) {
Console::WriteLine("Can only deal the {0} cards remaining on the deck.",
ctr + 1);
return cardsDealt;
}
}
return cardsDealt;
}
};

void ShowCards(array<Card^>^ cards)
{
for each (Card^ card in cards)
if (card != nullptr)
Console::WriteLine("{0} of {1}", card->FaceValue, card->Suit);
};

void main()
{
Dealer^ dealer = gcnew Dealer();
ShowCards(dealer->Deal(20));
}

// The example displays output like the following:
//       Six of Diamonds
//       King of Clubs
//       Eight of Clubs
//       Seven of Clubs
//       Queen of Clubs
//       King of Hearts
//       Three of Spades
//       Ace of Clubs
//       Four of Hearts
//       Three of Diamonds
//       Nine of Diamonds
//       Two of Hearts
//       Ace of Hearts
//       Three of Hearts
//       Four of Spades
//       Eight of Hearts
//       Queen of Diamonds
//       Two of Clubs
//       Four of Diamonds
//       Jack of Hearts
using System;

// A class that represents an individual card in a playing deck.
public class Card
{
public Suit Suit;
public FaceValue FaceValue;

public override String ToString()
{
return String.Format("{0:F} of {1:F}", this.FaceValue, this.Suit);
}
}

public enum Suit { Hearts, Diamonds, Spades, Clubs };

public enum FaceValue  { Ace = 1, Two, Three, Four, Five, Six,
Seven, Eight, Nine, Ten, Jack, Queen,
King };

public class Dealer
{
Random rnd;
// A deck of cards, without Jokers.
Card[] deck = new Card[52];
// Parallel array for sorting cards.
Double[] order = new Double[52];
// A pointer to the next card to deal.
int ptr = 0;
// A flag to indicate the deck is used.
bool mustReshuffle = false;

public Dealer()
{
rnd = new Random();
// Initialize the deck.
int deckCtr = 0;
foreach (var suit in Enum.GetValues(typeof(Suit))) {
foreach (var faceValue in Enum.GetValues(typeof(FaceValue))) {
Card card = new Card();
card.Suit = (Suit) suit;
card.FaceValue = (FaceValue) faceValue;
deck[deckCtr] = card;
deckCtr++;
}
}

for (int ctr = 0; ctr < order.Length; ctr++)
order[ctr] = rnd.NextDouble();

Array.Sort(order, deck);
}

public Card[] Deal(int numberToDeal)
{
if (mustReshuffle) {
Console.WriteLine("There are no cards left in the deck");
return null;
}

Card[] cardsDealt = new Card[numberToDeal];
for (int ctr = 0; ctr < numberToDeal; ctr++) {
cardsDealt[ctr] = deck[ptr];
ptr++;
if (ptr == deck.Length)
mustReshuffle = true;

if (mustReshuffle & ctr < numberToDeal - 1) {
Console.WriteLine("Can only deal the {0} cards remaining on the deck.",
ctr + 1);
return cardsDealt;
}
}
return cardsDealt;
}
}

public class Example
{
public static void Main()
{
Dealer dealer = new Dealer();
ShowCards(dealer.Deal(20));
}

private static void ShowCards(Card[] cards)
{
foreach (var card in cards)
if (card != null)
Console.WriteLine("{0} of {1}", card.FaceValue, card.Suit);
}
}
// The example displays output like the following:
//       Six of Diamonds
//       King of Clubs
//       Eight of Clubs
//       Seven of Clubs
//       Queen of Clubs
//       King of Hearts
//       Three of Spades
//       Ace of Clubs
//       Four of Hearts
//       Three of Diamonds
//       Nine of Diamonds
//       Two of Hearts
//       Ace of Hearts
//       Three of Hearts
//       Four of Spades
//       Eight of Hearts
//       Queen of Diamonds
//       Two of Clubs
//       Four of Diamonds
//       Jack of Hearts
' A class that represents an individual card in a playing deck.
Public Class Card
Public Suit As Suit
Public FaceValue As FaceValue

Public Overrides Function ToString() As String
Return String.Format("{0:F} of {1:F}", Me.FaceValue, Me.Suit)
End Function
End Class

Public Enum Suit As Integer
Hearts = 0
Diamonds = 1
Spades = 2
Clubs = 3
End Enum

Public Enum FaceValue As Integer
Ace = 1
Two = 2
Three = 3
Four = 4
Five = 5
Six = 6
Seven = 7
Eight = 8
Nine = 9
Ten = 10
Jack = 11
Queen = 12
King = 13
End Enum

Public Class Dealer
Dim rnd As Random
' A deck of cards, without Jokers.
Dim deck(51) As Card
' Parallel array for sorting cards.
Dim order(51) As Double
' A pointer to the next card to deal.
Dim ptr As Integer = 0
' A flag to indicate the deck is used.
Dim mustReshuffle As Boolean

Public Sub New()
rnd = New Random()
' Initialize the deck.
Dim deckCtr As Integer = 0
For Each Suit In [Enum].GetValues(GetType(Suit))
For Each faceValue In [Enum].GetValues(GetType(FaceValue))
Dim card As New Card()
card.Suit = CType(Suit, Suit)
card.FaceValue = CType(faceValue, FaceValue)
deck(deckCtr) = card
deckCtr += 1
Next
Next
For ctr As Integer = 0 To order.Length - 1
order(ctr) = rnd.NextDouble()
Next
Array.Sort(order, deck)
End Sub

Public Function Deal(numberToDeal As Integer) As Card()
If mustReshuffle Then
Console.WriteLine("There are no cards left in the deck")
Return Nothing
End If

Dim cardsDealt(numberToDeal - 1) As Card
For ctr As Integer = 0 To numberToDeal - 1
cardsDealt(ctr) = deck(ptr)
ptr += 1
If ptr = deck.Length Then
mustReshuffle = True
End If
If mustReshuffle And ctr < numberToDeal - 1
Console.WriteLine("Can only deal the {0} cards remaining on the deck.",
ctr + 1)
Return cardsDealt
End If
Next
Return cardsDealt
End Function
End Class

Public Module Example
Public Sub Main()
Dim dealer As New Dealer()
ShowCards(dealer.Deal(20))
End Sub

Private Sub ShowCards(cards() As Card)
For Each card In cards
If card IsNot Nothing Then _
Console.WriteLine("{0} of {1}", card.FaceValue, card.Suit)
Next
End Sub
End Module
' The example displays output like the following:
'       Six of Diamonds
'       King of Clubs
'       Eight of Clubs
'       Seven of Clubs
'       Queen of Clubs
'       King of Hearts
'       Three of Spades
'       Ace of Clubs
'       Four of Hearts
'       Three of Diamonds
'       Nine of Diamonds
'       Two of Hearts
'       Ace of Hearts
'       Three of Hearts
'       Four of Spades
'       Eight of Hearts
'       Queen of Diamonds
'       Two of Clubs
'       Four of Diamonds
'       Jack of Hearts

## Notas aos Herdeiros

No .NET Framework 1,0 e 1,1, uma implementação mínima de uma classe derivada da Random substituição necessária do Sample() método para definir um algoritmo novo ou modificado para gerar números aleatórios.In the .NET Framework 1.0 and 1.1, a minimum implementation of a class derived from Random required overriding the Sample() method to define a new or modified algorithm for generating random numbers. A classe derivada poderia então contar com a implementação da classe base dos Next() métodos,, Next(Int32) Next(Int32, Int32) , NextBytes(Byte[]) e NextDouble() para chamar a implementação da classe derivada do Sample() método.The derived class could then rely on the base class implementation of the Next(), Next(Int32), Next(Int32, Int32), NextBytes(Byte[]), and NextDouble() methods to call the derived class implementation of the Sample() method.

No .NET Framework 2,0 e posterior, o comportamento dos Next() Next(Int32, Int32) métodos, e foi NextBytes(Byte[]) alterado para que esses métodos não chamem necessariamente a implementação da classe derivada do Sample() método.In the .NET Framework 2.0 and later, the behavior of the Next(), Next(Int32, Int32), and NextBytes(Byte[]) methods have changed so that these methods do not necessarily call the derived class implementation of the Sample() method. Como resultado, as classes derivadas desse Random destino do .NET Framework 2,0 e posterior também devem substituir esses três métodos.As a result, classes derived from Random that target the .NET Framework 2.0 and later should also override these three methods.

## Notas aos Chamadores

A implementação do gerador de número aleatório na Random classe não tem garantia de permanecer a mesma em versões principais do .NET Framework.The implementation of the random number generator in the Random class isn't guaranteed to remain the same across major versions of the .NET Framework. Como resultado, você não deve pressupor que a mesma semente resultará na mesma sequência pseudo aleatória em diferentes versões do .NET Framework.As a result, you shouldn't assume that the same seed will result in the same pseudo-random sequence in different versions of the .NET Framework.

## Construtores

 Inicializa uma nova instância da classe Random usando um valor de semente padrão.Initializes a new instance of the Random class using a default seed value. Inicializa uma nova instância da classe Random, usando o valor de semente especificado.Initializes a new instance of the Random class, using the specified seed value.

## Métodos

 Determina se o objeto especificado é igual ao objeto atual.Determines whether the specified object is equal to the current object. (Herdado de Object) Serve como a função de hash padrão.Serves as the default hash function. (Herdado de Object) Obtém o Type da instância atual.Gets the Type of the current instance. (Herdado de Object) Cria uma cópia superficial do Object atual.Creates a shallow copy of the current Object. (Herdado de Object) Retorna um inteiro aleatório não negativo.Returns a non-negative random integer. Retorna um número inteiro aleatório não negativo menor que o máximo especificado.Returns a non-negative random integer that is less than the specified maximum. Retorna um inteiro aleatório que está dentro do intervalo especificado.Returns a random integer that is within a specified range. Preenche os elementos de uma matriz de bytes especificada com números aleatórios.Fills the elements of a specified array of bytes with random numbers. Preenche os elementos de um intervalo de bytes especificado com números aleatórios.Fills the elements of a specified span of bytes with random numbers. Retorna um número de ponto flutuante aleatório maior ou igual a 0,0 e menor que 1.0.Returns a random floating-point number that is greater than or equal to 0.0, and less than 1.0. Retorna um número de ponto flutuante aleatório entre 0.0 e 1.0.Returns a random floating-point number between 0.0 and 1.0. Retorna uma cadeia de caracteres que representa o objeto atual.Returns a string that represents the current object. (Herdado de Object)