设计模式之单例模式的多种使用方式

设计模式之单例模式

具体使用案例如下：

using System;
using System.Collections.Concurrent;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleTest
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("singleton。。。");

            var task = Enumerable.Range(1, 10).Select(i => Task.Run(() =>
              {
                  Console.WriteLine($"{SingleTon.Instance.GetHashCode()}");
              })).ToArray();

            Task.WaitAll(task);
            //Thread.Sleep(TimeSpan.FromSeconds(2));

            Console.WriteLine("SingleTon1");
            Enumerable.Range(1, 10).Select(i => Task.Run(() =>
            {
                Console.WriteLine($"{SingleTon1.Instance.GetHashCode()}");
            })).ToList();

            Thread.Sleep(TimeSpan.FromSeconds(2));
            Console.WriteLine("SingleTon2");
            Enumerable.Range(1, 10).Select(i => Task.Run(() =>
            {
                Console.WriteLine($"{SingleTon2.Instance.GetHashCode()}");
            })).ToList();
            Thread.Sleep(TimeSpan.FromSeconds(2));
            Console.WriteLine("SingleTon3");
            Enumerable.Range(1, 10).Select(i => Task.Run(() =>
            {
                Console.WriteLine($"{SingleTon3.Instance.GetHashCode()}");
            })).ToList();

            Thread.Sleep(TimeSpan.FromSeconds(2));
            Console.WriteLine("SingleTon4");
            Enumerable.Range(1, 10).Select(i => Task.Run(() =>
            {
                Console.WriteLine($"{SingleTon4.Instance.GetHashCode()}");
            })).ToList();

            Thread.Sleep(TimeSpan.FromSeconds(2));
            Console.WriteLine("SingleTon5");
            SingleTon5 singleTon5 = new SingleTon5();
            Enumerable.Range(1, 10).Select(i => Task.Run(() =>
            {
                Console.WriteLine($"{singleTon5.AddCount()}");
            })).ToList();

            Thread.Sleep(TimeSpan.FromSeconds(2));
            Console.WriteLine("SingleTon6");
            SingleTon6 singleTon6 = new SingleTon6();
            Enumerable.Range(1, 10).Select(i => Task.Run(() =>
            {
                Console.WriteLine($"{singleTon6.AddCount()}");
            })).ToList();

            Console.ReadLine();
        }
    }

    /// <summary>
    /// 单线程
    /// </summary>
    public class SingleTon
    {
        /// <summary>
        /// 私有变量，延迟加载
        /// </summary>
        private static SingleTon instance = null;

        /// <summary>
        /// 私有构造函数，方式初始化
        /// </summary>
        private SingleTon()
        {
        }

        /// <summary>
        /// 公开实例，单例供外部使用
        /// </summary>
        public static SingleTon Instance
        {
            get
            {
                if (instance == null)
                {
                    instance = new SingleTon();
                }
                return instance;
            }
        }
    }

    /// <summary>
    /// 多线程
    /// </summary>
    public class SingleTon1
    {
        /// <summary>
        /// 私有变量,提前初始化
        /// </summary>
        private static SingleTon1 instance = new SingleTon1();

        /// <summary>
        /// 私有构造函数，方式初始化
        /// </summary>
        private SingleTon1()
        {
        }

        /// <summary>
        /// 公开实例，单例供外部使用
        /// </summary>
        public static SingleTon1 Instance => instance;
    }

    /// <summary>
    /// 多线程
    /// </summary>
    public class SingleTon2
    {
        /// <summary>
        /// 私有变量,提前初始化
        /// </summary>
        private static SingleTon2 instance = null;
        /// <summary>
        /// 锁
        /// </summary>
        private static readonly object objectlock = new object();

        /// <summary>
        /// 私有构造函数，方式初始化
        /// </summary>
        private SingleTon2()
        {
        }

        /// <summary>
        /// 公开实例，单例供外部使用
        /// </summary>
        public static SingleTon2 Instance
        {
            get
            {
                if (instance == null)
                {
                    lock (objectlock)
                    {
                        if (instance == null)
                        {
                            instance = new SingleTon2();
                        }
                    }
                }
                return instance;
            }
        }
    }

    /// <summary>
    /// 多线程,并发字典
    /// </summary>
    public class SingleTon3
    {
        /// <summary>
        /// 并发字典
        /// </summary>
        private static readonly ConcurrentDictionary<int, SingleTon3> valuePairs = new ConcurrentDictionary<int, SingleTon3>();

        /// <summary>
        /// 私有构造函数，方式初始化
        /// </summary>
        private SingleTon3()
        {
        }

        /// <summary>
        /// 公开实例，单例供外部使用
        /// </summary>
        //public static SingleTon3 Instance => valuePairs.GetOrAdd(1, new SingleTon3());
        public static SingleTon3 Instance => valuePairs.GetOrAdd(1, k => new SingleTon3());
    }

    /// <summary>
    /// 多线程,并发字典
    /// </summary>
    public class SingleTon4
    {
        /// <summary>
        /// 并发字典
        /// </summary>
        //private static readonly Lazy<SingleTon4> singleTon = new Lazy<SingleTon4>();

        private static readonly Lazy<SingleTon4> singleTon = new Lazy<SingleTon4>(() => new SingleTon4());
        /// <summary>
        /// 私有构造函数，方式初始化
        /// </summary>
        private SingleTon4()
        {
        }

        /// <summary>
        /// 公开实例，单例供外部使用
        /// </summary>
        public static SingleTon4 Instance => singleTon.Value;
    }

    /// <summary>
    /// 多线程,原子操作
    /// </summary>
    public class SingleTon5
    {
        private int count;

        public int AddCount()
        {
            return Interlocked.Increment(ref count);
        }
    }


    /// <summary>
    /// 多线程,同步操作
    /// </summary>
    public class SingleTon6
    {
        private volatile int count;

        public int AddCount()
        {
            return count++;
        }
    }

}

运行效果如下：

原文连接：https://mp.weixin.qq.com/s?__biz=MzAwNTMxMzg1MA==&mid=2654079274&idx=5&sn=8cd230df2eb56e24eda99e8d78acc4b9&chksm=80d82d7fb7afa4696e1abaadd87786dbd62daaf94305bee8636cf4e4b6f477dcdd98e0d1dedb&scene=126&sessionid=1594862036&key=4169007045069748d1504711cd14df9bc2c208d234a13dcc2c89890f48b074d7e409342312d8fa1ca506d74e2dfed11179dedbb6964ec2771a33928a75bf65336f28383f7b2619103d73f2e03478d048&ascene=1&uin=MTUyNTkzNjE0MA%3D%3D&devicetype=Windows+Server+2016+x64&version=62090529&lang=zh_CN&exportkey=AYQKcVXwxpCQ3oUt7uD8mME%3D&pass_ticket=whN8iM%2F9O%2BA7ccmpvwHSqTQ%2BzUZoJMXE52%2B%2BDopvS%2FaUtZCM7jc0aTK7vNDUZaCd