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==Custom exception class==

<source lang="cpp">#include <iostream>
#include <string>
using namespace std;
class Exception {
public:
Exception(const string& msg) : msg_(msg) {}
~Exception( ) {}
string getMessage( ) const {return(msg_);}
private:
string msg_;
};
void f( ) {
throw(Exception("Mr. Sulu"));
}
int main( ) {
try {
f( );
}
catch(Exception& e) {
cout << "You threw an exception: " << e.getMessage( ) << endl;
}
}</source>
<pre class=codeResult>You threw an exception: Mr. Sulu</pre>

==Throw a custom exception object==

<source lang="cpp">#include <iostream>
using std::cout;
using std::endl;
class Trouble {
public:
Trouble(const char* pStr = "There"s a problem") : pMessage(pStr) {}
const char* what() const {return pMessage;}
private:
const char* pMessage;
};
int main() {
for(int i = 0 ; i < 2 ; i++) {
try {
if(i == 0)
throw Trouble();
else
throw Trouble("Nobody knows the trouble I"ve seen...");
}
catch(const Trouble& t) {
cout << endl << "Exception: " << t.what();
}
}
return 0;
}</source>
<pre class=codeResult>Exception: There"s a problem
Exception: Nobody knows the trouble I"ve seen..."</pre>

==Throw your own exception class based on runtime_error==

<source lang="cpp">#include <iostream>
#include <stdexcept>
using std::cin;
using std::cout;
using std::endl;
using std::runtime_error;
class DivideByZeroException : public runtime_error
{
public:
DivideByZeroException::DivideByZeroException(): runtime_error( "attempted to
divide by zero" ) {}
};
double quotient( int numerator, int denominator )
{
throw DivideByZeroException(); // terminate function
return 0;
}
int main()
{
try
{
double result = quotient( 1, 1 );
cout << "The quotient is: " << result << endl;
}
catch ( DivideByZeroException &divideByZeroException )
{
cout << "Exception occurred: " << divideByZeroException.what() << endl;
}
return 0;
}</source>
<pre class=codeResult>Exception occurred: attempted to divide by zero</pre>

==Use custom exception in your own Array class==

<source lang="cpp">#include <iostream>

const int DefaultSize = 10;

// define the exception classes
class ArrayIndexOutofBoundException {};

class BaseArraySizeException
{
public:
BaseArraySizeException(int size):itsSize(size) {}
~BaseArraySizeException(){}
virtual int GetSize() { return itsSize; }
virtual void PrintError()
{ std::cout << "Size error. Received: "
<< itsSize << std::endl; }
protected:
int itsSize;
};

class ArraySizeTooBigException : public BaseArraySizeException
{
public:
ArraySizeTooBigException(int size):BaseArraySizeException(size){}
virtual void PrintError()
{
std::cout << "Too big! Received: ";
std::cout << BaseArraySizeException::itsSize << std::endl;
}
};

class ArraySizeTooSmallException : public BaseArraySizeException
{
public:
ArraySizeTooSmallException(int size):BaseArraySizeException(size){}
virtual void PrintError()
{
std::cout << "Too small! Received: ";
std::cout << BaseArraySizeException::itsSize << std::endl;
}
};

class ArraySizeZeroException : public ArraySizeTooSmallException
{
public:
ArraySizeZeroException(int size):ArraySizeTooSmallException(size){}
virtual void PrintError()
{
std::cout << "Zero!!. Received: ";
std::cout << BaseArraySizeException::itsSize << std::endl;
}
};

class ArraySizeNegativeException : public BaseArraySizeException
{
public:
ArraySizeNegativeException(int size):BaseArraySizeException(size){}
virtual void PrintError()
{
std::cout << "Negative! Received: ";
std::cout << BaseArraySizeException::itsSize << std::endl;
}
};

class Array
{
public:
// constructors
Array(int itsSize = DefaultSize);
Array(const Array &rhs);
~Array() { delete [] pType;}

// operators
Array& operator=(const Array&);
int& operator[](int offSet);
const int& operator[](int offSet) const;

// accessors
int GetitsSize() const { return itsSize; }

// friend function
friend std::ostream& operator<< (std::ostream&, const Array&);

private:
int *pType;
int itsSize;
};

Array::Array(int size):
itsSize(size)
{
if (size == 0)
throw ArraySizeZeroException(size);

if (size < 0)
throw ArraySizeNegativeException(size);

if (size < 10)
throw ArraySizeTooSmallException(size);

if (size > 30000)
throw ArraySizeTooBigException(size);

pType = new int[size];
for (int i = 0; i<size; i++)
pType[i] = 0;
}

int& Array::operator[] (int offset)
{
int size = GetitsSize();
if (offset >= 0 && offset < GetitsSize())
return pType[offset];
throw ArrayIndexOutofBoundException();
return pType[offset];
}

const int& Array::operator[] (int offset) const
{
int size = GetitsSize();
if (offset >= 0 && offset < GetitsSize())
return pType[offset];
throw ArrayIndexOutofBoundException();
return pType[offset];
}

int main()
{
try
{
int choice;
std::cout << "Enter the array size: ";
std::cin >> choice;
Array intArray(choice);
for (int j = 0; j< 100; j++)
{
intArray[j] = j;
std::cout << "intArray[" << j << "] okay..."
<< std::endl;
}
}
catch (ArrayIndexOutofBoundException)
{
std::cout << "Unable to process your input!\n";
}
catch (BaseArraySizeException& theException)
{
theException.PrintError();
}
catch (...)
{
std::cout << "Something went wrong,"
<< "but I"ve no idea what!" << std::endl;
}
std::cout << "Done.\n";
return 0;
}</source>
<pre class=codeResult>Enter the array size: 12
intArray[0] okay...
intArray[1] okay...
intArray[2] okay...
intArray[3] okay...
intArray[4] okay...
intArray[5] okay...
intArray[6] okay...
intArray[7] okay...
intArray[8] okay...
intArray[9] okay...
intArray[10] okay...
intArray[11] okay...
Unable to process your input!
Done.</pre>

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