oo第三单元总结

oo第三单元总结

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架构设计

• 模型

  • 

• 维护策略

  • 属性：
    • 因无法预估输入指令，只维护较好维护的属性，如AgeSum等
  • 关系：
    • 因输入指令仅限制条数，对节点二重遍历的复杂度远高于对边的遍历，故需维护每个节点的边集Edges。
    • 连通性的检测最好采用并查集，故须维护人物关系树PeopleTree

性能分析

• 查询集合内部属性：由于维护了边集，而不用二重遍历节点，最多只需一重循环即可得到结果。同时维护的属性也可以达到1的复杂度
• 连通分量：采用并查集实现，就算不进行路径优化复杂度也最多为n
• 最小生成树：采用Prim算法，同时由于维护每个节点的边集优化了边的查找，复杂度也大概是n的量级
• 最短路径：与最小生成树十分类似

测试

• 性能测试：只进行分析，并无直接测试
• 功能测试：生成随机指令对拍

总结

• 本单元的思维难度大幅降低，最难的也只是那几个图算法的实现，但这种设计方式却十分值得我们学习。一方面JML无二义性的解析了需求，保证了客观需求到代码需求的正确性。另一方面这种由宏观到微观的设计思想逻辑上很通顺，不会出现各种重构的问题。此外这种只关心前提，约束的特点也很好的体现了封装性，每一模块只实现每一模块的功能，写起代码来很好上手。

扩展

• 向个人投放广告

  /*@public normal_behavior
      @requires contains(id1) && getPerson(id1) instanceof Advertiser && containsMessage(id2) && getMessage(id2) instanceof AdvertiseMessage;
      @assignable messages;
      @assinable getPerson(id1).advertisement[];
      @assinable getPerson(id2).preference[];
      @ensures !containsMessage(id2) && messages.length == \old(messages.length) - 1 && 
      @(\forall int i; 0 <= i && i < \old(messages.length) 
      	&& \old(messages[i].getId()) != id;
      @(\exists int j; 0 <= j && j < messages.length;
      	messages[j] == (\old(messages[i])));
      	
      @ensures (\forall int i; 0 <= i && i < (\old(getPerson(id1).advertisement.length)));
      @    (\exists int j; 0 <= j && j < getPerson(id1).advertisement.length; 				
      @	        getPerson(id1).advertisement[j] == (\old(getPerson(id1).advertisement.[i]))); 
  	
      @ensures (\exists int i; 0 <= i && i < getPerson(id1).advertisement.length); 		
      @    getPerson(id1).advertisement[i] == getMessage(id2))
  	
      @ensures (\exists int i; 0 <= i && i < \old(getPerson(id1).advertisement.length; 	 
      @(\old(getPerson(id1).advertisement.[i])) == getMessage(id2)) ==>
      @    getPerson(id1).advertisement.length == 										   	         
      @    (\old(getPerson(id1).advertisement.length)) && 
      @	   getPerson(id1).preference.length ==      				 	   	       	                    
      @    (\old(getPerson(id1).preference.length)) && 
      @	   getPerson(id1).preference[i] == \old(getPerson(id1).preference[i]) + 1;
  	
      @ensures (\forall int i; 0 <= i && i < \old(getPerson(id1).advertisement.length; 	 
      @(\old(getPerson(id1).advertisement.[i])) != getMessage(id2)) ==>
      @    getPerson(id1).advertisement.length == 										   	       
      @    (\old(getPerson(id1).advertisement.length)) + 1 && 
      @    getPerson(id1).preference.length ==		     				 	   	       	               
      @    (\old(getPerson(id1).preference.length)) + 1 && 
      @	   (\exists int i; 0 <= i && i < getPerson(id1).advertisement.length); 		     		      
      @    getPerson(id1).advertisement[i] == getMessage(id2)) &&
      @    getPerson(id1).preference[i] == 1;
  	 
      @also
      @public exceptional_behavior
      @signals (MessageIdNotFoundException e) !containsMessage(id);
      @signals (PersonIdNotFoundException e) !contains(id1);
      */
  public void advertise(int id1, int id2) throws MessageIdNotFoundException, PersonIdNotFoundException
  

• 生产产品

      /*@ public normal_behavior
        @ requires contains(producerId) && (getPerson(producerId) instanceof Producer);
        @ assignable getProducer(producerId).productList
        @ ensures getProdectCount(productId)
        @ ensures getProducer(producerId).getProductCount(productId) ==
        @           \old(getProducer(producerId).getProductCount(productId)) + 1;
        @ also
        @ public exceptional_behavior
        @ signals (PersonIdNotFoundException e) !contains(producerId);
        @ signals (NotProducerException e) !(getPerson(producerId) instanceof Producer);
        @*/
      public void Produce(int producerId, int productId) throws
              PersonIdNotFoundException, NotProducerException;
  

• 购买商品

  	/*@ public normal_behaviour
  	  @ requires message instanceof purchaseMessage;
  	  @ requires contains(advertiserId) && 
  	  @ (getPerson(advertiserId) instanceof Advertiser);
          @ requires !getPerson(advertiserId).containsMessage(message.getId())
  	  
    	  @ assignable getPerson(advertiserId).message[];
   	  @ ensuers getPerson(advertiserId).message.length == \old(getPerson(advertiserId).message.length) &&                
          @ getPerson(advertiserId).containsMessage(message.getId());
   	  @ also
          @ public exceptional_behavior
          @ signals (PersonIdNotFoundException e) !contains(advertiserId);
          @ signals (WrongMessageTypeException e) !(message instanceof purchaseMessage);
          @*/
  void purchase(int advertiserId, Message message) throws
              PersonIdNotFoundException, WrongMessageTypeException;