1、策略模式（Strategy）

 1 //抽象接口
 2 class ReplaceAlgorithm
 3 {
 4 public:
 5     virtual void Replace() = 0;
 6 };
 7 //三种具体的替换算法
 8 class LRU_ReplaceAlgorithm : public ReplaceAlgorithm
 9 {
10 public:
11     void Replace() { cout<<"Least Recently Used replace algorithm"<<endl; }
12 };
13
14 class FIFO_ReplaceAlgorithm : public ReplaceAlgorithm
15 {
16 public:
17     void Replace() { cout<<"First in First out replace algorithm"<<endl; }
18 };
19 class Random_ReplaceAlgorithm: public ReplaceAlgorithm
20 {
21 public:
22     void Replace() { cout<<"Random replace algorithm"<<endl; }
23 };  

 1 //Cache需要用到替换算法
 2 enum RA {LRU, FIFO, RANDOM}; //标签
 3 class Cache
 4 {
 5 private:
 6     ReplaceAlgorithm *m_ra;
 7 public:
 8     Cache(enum RA ra)
 9     {
10         if(ra == LRU)
11             m_ra = new LRU_ReplaceAlgorithm();
12         else if(ra == FIFO)
13             m_ra = new FIFO_ReplaceAlgorithm();
14         else if(ra == RANDOM)
15             m_ra = new Random_ReplaceAlgorithm();
16         else
17             m_ra = NULL;
18     }
19     ~Cache() { delete m_ra; }
20     void Replace() { m_ra->Replace(); }
21 };  

1 int main()
2 {
3     Cache cache(LRU); //指定标签即可
4     cache.Replace();
5     return 0;
6 }