享元模式

享元模式：让一个对象共享。

场景：String池。

UML图：

示例代码：

    public abstract class Flyweight
    {
        public abstract void Operation();
    }

    public class ConcreteFlyweight:Flyweight
    {
        public override void Operation()
        {
            Console.WriteLine("Run");
        }
    }

    public class FlywightFactory
    {
        Dictionary<string, ConcreteFlyweight>  dictionary = new Dictionary<string, ConcreteFlyweight>();

        public ConcreteFlyweight GetFlyweight(string key)
        {
            if (dictionary.Keys.Contains(key))
            {
                return dictionary[key];
            }
            var fly = new ConcreteFlyweight();
            dictionary.Add(key, fly);
            return fly;
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            FlywightFactory factory = new FlywightFactory();
            var fac = factory.GetFlyweight("chenyishi");
            fac = factory.GetFlyweight("chenyishi");
        }
    }