C++ Exception handler with multiple catch blocks

Introduction

We can have/raise multiple exceptions.

They can be of different types.

In this case, we have one try and multiple catch blocks.

Each catch block handles a different exception. 

#include <iostream> 
#include <string> 

int main() //from   w w  w  .  j  av a 2 s .c  o  m
{ 
    try 
    { 
        throw 123; 
        // the following will not execute as 
        // the control has been transferred to a catch clause 
        throw std::string{ "Some string error" }; 
    } 
    catch (int e) 
    { 
        std::cout << "Integer exception raised! The value is " << e << '\n'; 
    } 
    catch (const std::string& e) 
    { 
        // catch and handle the exception 
        std::cout << "String exception raised!." << '\n'; 
        std::cout << "The exception has a value of: " << e << '\n'; 
    } 
}

Here we throw multiple exceptions in the try block.

The first is of type int, and the second is of std::string type.

The moment the first exception is thrown, the control of the program is transferred to a catch clause.

This means that the remainder of the code inside the try block will not be executed.

A more realistic scenario would be: 

#include <iostream> 
#include <string> 

int main() //w ww . j  av a 2  s.  c  om
{ 
    try 
    { 
        bool someflag = true; 
        bool someotherflag = true; 
        std::cout << "We can have multiple throw exceptions." << '\n'; 
        if (someflag) 
        { 
            std::cout << "Throwing an int exception." << '\n'; 
            throw 123; 
        } 
        if(someotherflag) 
        { 
            std::cout << "Throwing a string exception." << '\n'; 
            throw std::string{ "Some string error" }; 
        } 
    } 
    catch (int e) 
    { 
        // catch and handle the exception 
        std::cout << "Integer exception raised!." << '\n'; 
        std::cout << "The exception has a value of: " << e << '\n'; 
    } 

    catch (const std::string& e) 
    { 
        // catch and handle the exception 
        std::cout << "String exception raised!." << '\n'; 
        std::cout << "The exception has a value of: " << e << '\n'; 
    } 
}

Here we throw multiple exceptions inside the try block.

They depend on some if conditions for illustrative purposes.

When a first exception is encountered, the control is transferred to an appropriate catch clause.




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