迭代器模式

一、今日学习内容

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。

类图：

 

测试结果：

  

 c++：

#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;
    for(int i=1;i<=44;i++)
    {
        int m=20130000+i;
        objects->AddObject(m); 
        m=0;
    }
 
    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;  
}