// "Charactor" public abstract class Charactor {     //Fields     protected char _symbol;       protected int _width;       protected int _height;       protected int _ascent;       protected int _descent;       protected int _pointSize;       //Method     public abstract void SetPointSize(int size);     public abstract void Display(); }   // "CharactorA" public class CharactorA : Charactor {     // Constructor     public CharactorA()     {         this._symbol = 'A';         this._height = 100;         this._width = 120;         this._ascent = 70;         this._descent = 0;     }       //Method     public override void SetPointSize(int size)     {         this._pointSize = size;     }       public override void Display()     {         Console.WriteLine(this._symbol +           "pointsize:" + this._pointSize);     } }   // "CharactorB" public class CharactorB : Charactor {     // Constructor     public CharactorB()     {         this._symbol = 'B';         this._height = 100;         this._width = 140;         this._ascent = 72;         this._descent = 0;     }       //Method     public override void SetPointSize(int size)     {         this._pointSize = size;     }       public override void Display()     {         Console.WriteLine(this._symbol +           "pointsize:" + this._pointSize);     } }   // "CharactorC" public class CharactorC : Charactor {     // Constructor     public CharactorC()     {         this._symbol = 'C';         this._height = 100;         this._width = 160;         this._ascent = 74;         this._descent = 0;     }       //Method     public override void SetPointSize(int size)     {         this._pointSize = size;     }       public override void Display()     {         Console.WriteLine(this._symbol +           "pointsize:" + this._pointSize);     } }   // "CharactorFactory" public class CharactorFactory {     // Fields     private Hashtable charactors = new Hashtable();       // Constructor     public CharactorFactory()     {         charactors.Add("A", new CharactorA());         charactors.Add("B", new CharactorB());         charactors.Add("C", new CharactorC());     }            // Method     public Charactor GetCharactor(string key)     {         Charactor charactor = charactors[key] as Charactor;           if (charactor == null)         {             switch (key)             {                 case "A": charactor = new CharactorA(); break;                 case "B": charactor = new CharactorB(); break;                 case "C": charactor = new CharactorC(); break;                 //             }             charactors.Add(key, charactor);         }         return charactor;     } }   public class Program {     public static void Main()     {         CharactorFactory factory = new CharactorFactory();           // Charactor "A"         CharactorA ca = (CharactorA)factory.GetCharactor("A");         ca.SetPointSize(12);         ca.Display();                 // Charactor "B"         CharactorB cb = (CharactorB)factory.GetCharactor("B");         ca.SetPointSize(10);         ca.Display();           // Charactor "C"         CharactorC cc = (CharactorC)factory.GetCharactor("C");         ca.SetPointSize(14);         ca.Display();     } }

可以看到这样的实现明显优于第一种实现思路。好了，到这里我们就到到了通过Flyweight模式实现了优化资源的这样一个目的。在这个过程中，还有如下几点需要说明：

1．引入CharactorFactory是个关键，在这里创建对象已经不是new一个Charactor对象那么简单，而必须用工厂方法封装起来。

2．在这个例子中把Charactor对象作为Flyweight对象是否准确值的考虑，这里只是为了说明Flyweight模式，至于在实际应用中，哪些对象需要作为Flyweight对象是要经过很好的计算得知，而绝不是凭空臆想。

3．区分内外部状态很重要，这是享元对象能做到享元的关键所在。

到这里，其实我们的讨论还没有结束。有人可能会提出如下问题，享元对象（Charactor）在这个系统中相对于每一个内部状态而言它是唯一的，这跟单件模式有什么区别呢？这个问题已经很好回答了，那就是单件类是不能直接被实例化的，而享元类是可以被实例化的。事实上在这里面真正被设计为单件的应该是享元工厂（不是享元）类，因为如果创建很多个享元工厂的实例，那我们所做的一切努力都是白费的，并没有减少对象的个数。修改后的类结构图如下：

图9

示意性实现代码：