template《class T》到底怎么用呢！

对内置的 和 typedef 的感觉差不多
照着抄的：
#include <iostream>
#include <cstdlib>
using namespace std;

class student
{
private:
    int id;
    float gpa;
public:
    student(int a = 4, float b = 5 ):id(a),gpa(b){}
/*    student(const student &s)
    {
        id = s.id;
        gpa = s.gpa;
    }
*/
    int Get(){ return id;}
};

template<class T>
class Store
{
private:
    T item;
    int haveValue;
public:
    Store(void);
    Store(T x);
    T GetElem(void);
    //void PutElem(T x);
};

template<class T>
Store<T>::Store(void):haveValue(0)
{}

template<class T>
Store<T>::Store( T x):haveValue(1), item(x)
{}

template<class T>
T Store<T>::GetElem(void)
{
    if( haveValue == 0 )
    {
        cout<<"No item present!"<<endl;
        exit(1);
    }
    return item;
}


/*template<class T>
void Store<T>::PutElem( T x )
{
    haveValue++;
    item = x;
}*/

int main()
{
    student g(1000, 23);
    Store<int> S1(2), S2(8);
    Store<student> S3(g);

    Store<double> D;
//    S1.PutElem(3);
//    S2.PutElem(7);

    cout<<S1.GetElem()<<" "<<S2.GetElem()<<endl;

//    S3.PutElem(g);
    cout<<"The student id is "<<S3.GetElem().Get()<<endl;

    return 0;
}