/// <summary>
  /// 錯(cuò)誤的Random構(gòu)建。
  /// </summary>
  public static void Bad_Random()
  {
    //正確做法應(yīng)當(dāng)將 Random構(gòu)建防止循環(huán)外。
    //Random創(chuàng)建間隔時(shí)間極短的情況下，隨機(jī)算法序列會(huì)基本一致，倒是隨機(jī)性也是一致的
    //var r = new Random();
    for (int i = 0; i < 10; i++)
    {
      var r = new Random();
      var val = r.Next(1, 100);
      Console.WriteLine(val);
    }
  }

  /// <summary>
  /// 生成一個(gè)10位隨機(jī)數(shù)
  /// 設(shè)定了一定的復(fù)雜性，保證單線程下隨機(jī)數(shù)不重復(fù)
  /// </summary>
  /// <param name="random">Random.</param>
  /// <returns>隨機(jī)數(shù).</returns>
  private static string GenerateRandomStr(Random random)
  {
    string source = "ABCDEFGHIKLMNOPQRTUVWXYZabcdefghiklmnopqrtuvwxyz";
    int length = 10;
    var list = Enumerable.Repeat(source, length)
       .Select(s => s[random.Next(s.Length)]).ToArray();
    return new string(list);
  }
  /// <summary>
  /// 單線程基本可以保證唯一性
  /// </summary>
  public static void Good_Random_In_SingleThread()
  {
    //正確做法應(yīng)當(dāng)將 Random構(gòu)建防止循環(huán)外。
    //Random創(chuàng)建間隔時(shí)間極短的情況下，隨機(jī)算法序列會(huì)基本一致，倒是隨機(jī)性也是一致的
    var r = new Random();
    ConcurrentBag<string> list = new ConcurrentBag<string>();
    for (int i = 0; i < 20000; i++)
    {
      var val = GenerateRandomStr(r);
      list.Add(val);
    }

    Console.WriteLine($"單線程下重復(fù)數(shù)據(jù)有：{20000 - list.Distinct().Count()}");
  }

  /// <summary>
  /// 多線程下的Random構(gòu)建。
  /// Bad案例，Random非線程安全
  /// 多線程高并發(fā)情況下，會(huì)出現(xiàn)概率重復(fù)
  /// </summary>
  public static void Bad_Random_In_MultThreads()
  {
    var r = new Random(unchecked((int)DateTime.Now.Ticks));
    ConcurrentBag<string> list = new ConcurrentBag<string>();

    var t1 = Task.Run(() =>
    {
      for (int i = 0; i < 10000; i++)
      {
        var val = GenerateRandomStr(r);
        list.Add(val);
      }
    });

    var t2 = Task.Run(() =>
    {
      for (int i = 0; i < 10000; i++)
      {
        var val = GenerateRandomStr(r);
        list.Add(val);
      }
    });

    Task.WaitAll(t1, t2);

    Console.WriteLine($"線程1和線程2的重復(fù)數(shù)據(jù)有：{20000 - list.Distinct().Count()}");
  }

 //利用ThreadLocal 實(shí)現(xiàn)每個(gè)線程下Random獨(dú)有
  //再通過seed原子性變更，保證每個(gè)Random的seed不同而生成的隨機(jī)數(shù)列也不同
  private static int seed = 100;
  private static ThreadLocal<Random> threadLocal = new ThreadLocal<Random>(() => new Random(Interlocked.Increment(ref seed)));

  /// <summary>
  /// 多線程下的Random構(gòu)建。
  /// </summary>
  public static void Good_Random_In_MultThreads()
  {
    ConcurrentBag<string> list = new ConcurrentBag<string>();

    var t1 = Task.Run(() =>
    {
      for (int i = 0; i < 10000; i++)
      {
        var val = GenerateRandomStr(threadLocal.Value);
        list.Add(val);
      }
    });

    var t2 = Task.Run(() =>
    {
      for (int i = 0; i < 10000; i++)
      {
        var val = GenerateRandomStr(threadLocal.Value);
        list.Add(val);
      }
    });

    Task.WaitAll(t1, t2);

    Console.WriteLine($"[ThreadLocal模式]線程1和線程2的重復(fù)數(shù)據(jù)有：{20000 - list.Distinct().Count()}");
  }