自定义异常类

C++自定义异常类，在抛出异常后必须去在可能发生异常的地方接收异常，如果只是抛出而不接收会报错

//Exception.h

#ifndef EXCEPTION_H
#define EXCEPTION_H
#include <string>
#include<sstream>
using namespace std;
class FirstException 
{
public:
    FirstException() {};
    FirstException(string str)
    {
        mes = str;
    }
    void outputMessage()
    {
        cout << mes;
    }
private:
    string mes;
};
class SecondException 
{
public:
    SecondException() {};
    SecondException(string str)
    {
        mes = str;
    }
    void outputMessage()
    {
        cout << mes;
    }
private:
    string mes;
};
class ThirdException 
{
public:
    ThirdException() {};
    ThirdException(string str)
    {
        mes = str;
    }
    void outputMessage()
    {
        cout << mes;
    }
private:
    string mes;
};

double addanddiv(double a, double b, double c)
{
    if (a < 0)
    {
        ostringstream s;
        s << "a的值为" << a << "   a应该大于0";
        throw FirstException(s.str());
    }

    if (b < 0)
    {
        ostringstream s;
        s << "b的值为" << b << "   b应该大于0";
        throw SecondException(s.str());
    }

    if (c < 0)
    {
        ostringstream s;
        s << "c的值为" << c << "   c应该大于0";
        throw ThirdException(s.str());
    }
    return((a + b) / c);
}



#endif // !EXCEPTION_H

//main
#include <iostream>
#include "Exception.h"

//using namespace std;

int main()
{
    try
    {
        //cout << addanddiv(-1, 2, 3) << endl;//测试异常一
        //cout << addanddiv(2, -2, 3) << endl;//测试异常二
        //cout << addanddiv(1, 3, -4) << endl;//测试异常三
        cout << addanddiv(3, 2, 3) << endl;
    }
    catch (FirstException e)
    {
        printf("异常一\n");
        e.outputMessage();
    }
    catch (SecondException e)
    {
        printf("异常二\n");
        e.outputMessage();
    }
    catch (ThirdException e)
    {
        printf("异常三\n");
        e.outputMessage();
    }
    return 0;
}