设计模式：单例模式

Posted 2020-06-24 uptothesky

单例模式（Singleton）：保证一个类仅有一个实例，并提供一个访问它的全局访问点。

懒汉式：

namespace SingletonDesign
{
    public class Singleton
    {
        private static Singleton instance;
        private static readonly object syncRoot = new object();
        private Singleton() { }
        public static Singleton GetInstance()
        {
            if(instance==null)
            {
                lock (syncRoot)
                {
                    if (instance == null)
                    {
                        instance = new Singleton();
                    }
                }
            }
            return instance;
        }
    }
}

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测试代码：

            for(int i=0;i<100;i++)
            {
                Task.Run(() => {
                    Singleton s = Singleton.GetInstance();
                    Console.WriteLine(s.GetHashCode());
                });
            }

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饿汉式：

namespace SingletonDesign
{
    public sealed class Singleton
    {
        private static readonly Singleton instance=new Singleton();
        private Singleton() { }
        public static Singleton GetInstance()
        {
            return instance;
        }
    }
}

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