单例模式

#include <iostream>
 
using namespace std;
 
class S_num{
private:
    static S_num sno;
    static int num;
public:
    static S_num getintance() {
       // TODO Auto-generated method stub
       if(num==0) {
           cout<<"第一次办理学生证，分配新号码！"<<endl;
           sno.setNum(20194171);
       }
       else {
           cout<<"重复办理学生证，获取旧号码！"<<endl;
       }
       return sno;
    }
    int getNum() {
       return num;
    }
    void setNum(int n) {
       num = n;
    }
};
 
int S_num::num = 0;
S_num S_num::sno = S_num();
 
 
int main()
{
    S_num sno1=S_num().getintance();
    cout<<"第一次获取学号"<<sno1.getNum()<<endl;
    S_num sno2=S_num().getintance();
    cout<<"第二次获取学号"<<sno2.getNum()<<endl;
    cout<<"内容是否相等："<<(sno1.getNum()==sno2.getNum())<<endl;
    //cout<<"是否是相同对象："<<(sno1==sno2)<<endl;
}


Main

public class Main {

    public static void main(String [] args) {

        S_num sno1=S_num.getintance();

        System.out.println("第一次获取学号"+sno1.getNum());

        S_num sno2=S_num.getintance();

        System.out.println("第二次获取学号"+sno2.getNum());

        System.out.println("内容是否相等：" + (sno1.getNum()==sno2.getNum()));

         System.out.println("是否是相同对象：" + (sno1==sno2));

    }

}
 

S_num

public class S_num  {

    private static S_num sno=null;

    private int num=0;

    private S_num() {

    }

    public static S_num getintance() {

        // TODO Auto-generated method stub

        if(sno==null) {

            System.out.println("第一次办理学生证，分配新号码！");

            sno=new S_num();

            sno.setNum(20183597);

        }

        else {

            System.out.println("重复办理学生证，获取旧号码！");

        }

        return sno;

    }

    public int getNum() {

        return num;

    }

    public void setNum(int num) {

        this.num = num;

    }

   

}