2021.11.24

今日学习内容：迭代器模式

信1305班共44名同学，每名同学都有姓名，学号和年龄等属性，分别使用JAVA内置迭代器和C++中标准模板库（STL）实现对同学信息的遍历，要求按照学号从小到大和从大到小两种次序输出学生信息。

c++源代码：

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#include <iostream>  #include<string> #include <sstream> #include <vector>  using namespace std;   /* object可以是任意类型的变量 */ typedef int object;   class Iterator { public:     virtual object begin() = 0;     virtual void   next() = 0;     virtual object end() = 0;     virtual object current() = 0;     virtual bool   IsDone() = 0; };   class ConcreteAggregate { private:     vector<object> _objects;   public:     void AddObject(object obj)     {         _objects.push_back(obj);     }       object& operator[](int index)     {         return _objects[index];     }     int size()     {         return _objects.size();     } };   class ConcreteIterator :public Iterator { public:     ConcreteAggregate *agg;     int _index; public:     ConcreteIterator(ConcreteAggregate *agg)     {         this->agg = agg;         _index = 0;     }     virtual object begin()     {         return (*agg)[0];     }     virtual void next()     {         _index++;     }     virtual void preious()     {         _index--;     }       virtual object end()     {         _index = agg->size();         return (*agg)[_index - 1];     }       virtual object current()     {         return (*agg)[_index];     }       virtual bool IsDone()     {         return (_index == agg->size());     }     virtual bool IsFirst()     {         return (_index == 0);     } };   int main() {     ConcreteAggregate *objects = new ConcreteAggregate();     cout << "信1305班同学:" << endl;     object a = 20130001;     object b = 20130002;     object c = 20130003;     object d = 20130004;     object e = 20130005;     object f = 20130006;     object g = 20130007;       objects->AddObject(a);     objects->AddObject(b);     objects->AddObject(c);     objects->AddObject(d);     objects->AddObject(e);     objects->AddObject(f);     objects->AddObject(g);         ConcreteIterator *iter = new ConcreteIterator(objects);     ConcreteIterator *iter1 = new ConcreteIterator(objects);       object tmp_begin = iter->begin();     cout << "从小到大输出:" << endl;     while (!iter->IsDone())     {         cout << iter->current() << endl;         iter->next();     }     cout << endl;       object tmp_begin1 = iter1->end();     cout << "从大到小输出:" << endl;     while (!iter1->IsFirst())     {         iter1->preious();         cout << iter1->current() << endl;     }     cout << endl;       delete objects;     delete iter;       system("pause");     return 0; }

　　

实现截图如下：