#include<iostream.h>
class Date
{
private:
    int day,month,year;
public:
    Date(int d,int m,int y)
    {
        day=d;
        month=m;
        year=y;
        cout<<day<<"/"<<month<<"/"<<year<<endl;
    };

    void add()
    {
        if(month>0 && month<13)
        {
            if(month==1||month==3||month==5||month==7||month==8||month==10)
            {
                if(day>0 && day<31)day++;else if(day==31){day=1;month++;}}
            else if(month==12)
            {
                if(day>0 && day<31)day++;else if(day==31){day=1;month=1;year++;}}
            else
            {
                if(day>0 && day<31)day++;else if(day==31){day=1;month++;}
        }
        cout<<day<<"/"<<month<<"/"<<year<<endl;
    };
}

    int main()
{
    Date date1(4,6,2015);
    date1.add();
}

贴出错误，不贴错误谁去给你检查标点符号

add函数连'}'都少了一个，怎么编译得过，iostream不加.h, 之后using namespace std;主函数返回0,这样才能通过编译。
#include<iostream>
using namespace std;
class Date
{
private:
    int day,month,year;
public:
    Date(int d,int m,int y)
    {
        day=d;
        month=m;
        year=y;
        cout<<day<<"/"<<month<<"/"<<year<<endl;
    };

    void add()
    {
        if(month>0 && month<13)
        {
            if(month==1||month==3||month==5||month==7||month==8||month==10)
            {
                if(day>0 && day<31)day++;
                else if(day==31){day=1;month++;}
            }
            else if(month==12)
            {
                if(day>0 && day<31)day++;
                else if(day==31){day=1;month=1;year++;}
            }
            else
            {
                if(day>0 && day<31)day++;else if(day==31){day=1;month++;}
            }
            cout<<day<<"/"<<month<<"/"<<year<<endl;
        }
    }
};

    int main()
{
    Date date1(4,6,2015);
    date1.add();
    return 0;
}

不好意思，第一次发帖，以后会注意的

多谢多谢！