Singleton设计模式与双重检查锁

Question

考虑一下你有以下代码:
1.为什么我们使用双重检查锁,为什么单锁不够好,请提供详细的例子.
2.这种实施的主要缺点是什么？我该如何证明呢？
谢谢.

 public sealed class SomeSingleton5  
{  
    private static SomeSingleton5 s_Instance = null;
    private static object s_LockObj = new Object();

    private SomeSingleton5() { }

    public static SomeSingleton5 Instance
    {
        get
        {
            if (s_Instance == null)
            {
                lock (s_LockObj)
                {
                    if (s_Instance == null)
                    {
                        s_Instance = new SomeSingleton5();
                    }
                }
            }

            return s_Instance;
        }
    }
}

Answer 1

我认为单例类的最佳实现是由提供的Jon Skeet.

public sealed class Singleton
{
  private static readonly Singleton instance = new Singleton();
  public static Singleton Instance { get { return instance; } }
  static Singleton() {}
  private Singleton() {}
}

单身人士由Jon Skeet澄清