关于C++的重载运算符和重载函数

#include <iostream>
using namespace std;
class printData
{
   public:
      void print(int i) {
        cout << "整数为: " << i << endl;
      }
      void print(double  f) {
        cout << "浮点数为: " << f << endl;
      }
      void print(char c[]) {
        cout << "字符串为: " << c << endl;
      }
};
int main(void)
{
   printData pd;
   // 输出整数
   pd.print(5);
   // 输出浮点数
   pd.print(500.263);
   // 输出字符串
   char c[] = "Hello C++";
   pd.print(c);
   return 0;

Box operator+(const Box&);

Box operator+(const Box&, const Box&);

#include <iostream>
using namespace std;
class Box
{
   public:
      double getVolume(void)
      {
         return length * breadth * height;
      }
      void setLength( double len )
      {
          length = len;
      }
      void setBreadth( double bre )
      {
          breadth = bre;
      }
      void setHeight( double hei )
      {
          height = hei;
      }
      // 重载 + 运算符，用于把两个 Box 对象相加
      Box operator+(const Box& b)
      {
         Box box;
         box.length = this->length + b.length;
         box.breadth = this->breadth + b.breadth;
         box.height = this->height + b.height;
         return box;
      }
   private:
      double length;      // 长度
      double breadth;     // 宽度
      double height;      // 高度
};
// 程序的主函数
int main( )
{
   Box Box1;                // 声明 Box1，类型为 Box
   Box Box2;                // 声明 Box2，类型为 Box
   Box Box3;                // 声明 Box3，类型为 Box
   double volume = 0.0;     // 把体积存储在该变量中
   // Box1 详述
   Box1.setLength(6.0); 
   Box1.setBreadth(7.0); 
   Box1.setHeight(5.0);
   // Box2 详述
   Box2.setLength(12.0); 
   Box2.setBreadth(13.0); 
   Box2.setHeight(10.0);
   // Box1 的体积
   volume = Box1.getVolume();
   cout << "Volume of Box1 : " << volume <<endl;
   // Box2 的体积
   volume = Box2.getVolume();
   cout << "Volume of Box2 : " << volume <<endl;
   // 把两个对象相加，得到 Box3
   Box3 = Box1 + Box2;
   // Box3 的体积
   volume = Box3.getVolume();
   cout << "Volume of Box3 : " << volume <<endl;
   return 0;
}