Конструкторы с++, перегрузка операторов

#include "Box.h"
 
 
Box::Box()
    :breadth(0), width(0), height(0)
{
}
 
Box::Box(int b,int w,int h)
{
    breadth = b;
    width = w;
    height = h;
}
 
void Box::setparam(int b, int w, int h)
{
    breadth = b;
    width = w;
    height = h;
}
 
Box Box::operator+(Box a)
{
    Box box;
    box.breadth = this->breadth + a.breadth;
    box.height = this->height + a.height;
    box.width = this->width + a.width;
    return box;
}
 
ostream &operator<<(ostream &out, Box &a)
{
    out << "The box length is " << a.breadth<<endl;
    out << "The box height is " << a.height<<endl;
    out << "The box width is " << a.width << endl;
    return out;
}
 
istream &operator>>(istream &in, Box &a)
{
    in >> a.breadth>>a.height>>a.width;
    return in;
}
Box Box::operator++(int)
{
    Box temp = *this;
    this->breadth++;
    this->width++;
    this->height++;
    return temp;
}
Box Box::operator++()
{
    this->breadth++;
    this->width++;
    this->height++;
    return *this;
}

Box a();
cout<< a;

Box a(1,1,1);
cout <<a;

Box a;