Question

I have a difficult to understand the subject of overloading operator in C++ and Java.

For example, I define a new class Fraction:

class Fraction { 
public: 
    Fraction (int top, int bottom) { t = top; b = bottom; } 
    int numerator() { return t; } 
    int denominator() { return b; } 
private: 
    int t, b; 
};

and I want to overload the operator << for printing Fraction. How I do it? I need to overload it inside Class Fraction or outside Class Fraction?

In java – Is it possible to overload operator? How I can do it there (for example, I want to overload the operator +).

If there is a metrial about this subject, It will be great.

Answer 1

For C++: Overloading the << Operator on msdn

// overload_date.cpp
// compile with: /EHsc
#include <iostream>
using namespace std;

class Date
{
    int mo, da, yr;
public:
    Date(int m, int d, int y)
    {
        mo = m; da = d; yr = y;
    }
    friend ostream& operator<<(ostream& os, const Date& dt);
};

ostream& operator<<(ostream& os, const Date& dt)
{
    os << dt.mo << '/' << dt.da << '/' << dt.yr;
    return os;
}

int main()
{
    Date dt(5, 6, 92);
    cout << dt;
}

So as answer to “I need to overload it inside Class Fraction or outside Class Fraction?”
You declare the function as a friend of the class so that the std::osteam object can access its private data. The function, however, is defined outside of the class.