目录

1.继承

#include <iostream>

using namespace std;

// 基类
class Shape 
{
   public:
      void setWidth(int w)
      {
         width = w;
      }
      void setHeight(int h)
      {
         height = h;
      }
   protected:
      int width;
      int height;
};

// 派生类
class Rectangle: public Shape
{
   public:
      int getArea()
      { 
         return (width * height); 
      }
};

int main(void)
{
   Rectangle Rect;

   Rect.setWidth(5);
   Rect.setHeight(7);

   // 输出对象的面积
   cout << "Total area: " << Rect.getArea() << endl;

   return 0;
}

当上面的代码被编译和执行时，它会产生下列结果：
Total area: 35

#include <iostream>

using namespace std;

// 基类 Shape
class Shape 
{
   public:
      void setWidth(int w)
      {
         width = w;
      }
      void setHeight(int h)
      {
         height = h;
      }
   protected:
      int width;
      int height;
};

// 基类 PaintCost
class PaintCost 
{
   public:
      int getCost(int area)
      {
         return area * 70;
      }
};

// 派生类
class Rectangle: public Shape, public PaintCost
{
   public:
      int getArea()
      { 
         return (width * height); 
      }
};

int main(void)
{
   Rectangle Rect;
   int area;

   Rect.setWidth(5);
   Rect.setHeight(7);

   area = Rect.getArea();

   // 输出对象的面积
   cout << "Total area: " << Rect.getArea() << endl;

   // 输出总花费
   cout << "Total paint cost: $" << Rect.getCost(area) << endl;

   return 0;
}

当上面的代码被编译和执行时，它会产生下列结果：
Total area: 35
Total paint cost: $2450

#include <iostream>

using namespace std;
//基类

class D
{
public:
    D(){cout<<"D()"<<endl;}
    ~D(){cout<<"~D()"<<endl;}
protected:
    int d;
};

class B:virtual public D
{
public:
    B(){cout<<"B()"<<endl;}
    ~B(){cout<<"~B()"<<endl;}
protected:
    int b;
};

class A:virtual public D
{
public:
    A(){cout<<"A()"<<endl;}
    ~A(){cout<<"~A()"<<endl;}
protected:
    int a;
};

class C:public B, public A
{
public:
    C(){cout<<"C()"<<endl;}
    ~C(){cout<<"~C()"<<endl;}
protected:
    int c;
};

int main()
{
    cout << "Hello World!" << endl;
    C c;   //D, B, A ,C
    cout<<sizeof(c)<<endl;
    return 0;
}

Hello World!
D()
B()
A()
C()
40
~C()
~A()
~B()
~D()

2.重载

#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(string 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
   pd.print("Hello C++");

   return 0;
}

当上面的代码被编译和执行时，它会产生下列结果：
整数为: 5
浮点数为: 500.263
字符串为: Hello C++

#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;
}

当上面的代码被编译和执行时，它会产生下列结果：
Volume of Box1 : 210
Volume of Box2 : 1560
Volume of Box3 : 5400

#include <iostream>
using namespace std;

class Distance
{
   private:
      int feet;             // 0 到无穷
      int inches;           // 0 到 12
   public:
      // 所需的构造函数
      Distance(){
         feet = 0;
         inches = 0;
      }
      Distance(int f, int i){
         feet = f;
         inches = i;
      }
      // 显示距离的方法
      void displayDistance()
      {
         cout << "F: " << feet << " I:" << inches <<endl;
      }
      // 重载负运算符（ - ）
      Distance operator- ()  
      {
         feet = -feet;
         inches = -inches;
         return Distance(feet, inches);
      }
};
int main()
{
   Distance D1(11, 10), D2(-5, 11);

   -D1;                     // 取相反数
   D1.displayDistance();    // 距离 D1

   -D2;                     // 取相反数
   D2.displayDistance();    // 距离 D2

   return 0;
}

当上面的代码被编译和执行时，它会产生下列结果：
F: -11 I:-10
F: 5 I:-11

3.多态 && 虚函数

#include <iostream> 
using namespace std;

class Shape {
   protected:
      int width, height;
   public:
      Shape( int a=0, int b=0)
      {
         width = a;
         height = b;
      }
      int area()
      {
         cout << "Parent class area :" <<endl;
         return 0;
      }
};
class Rectangle: public Shape{
   public:
      Rectangle( int a=0, int b=0):Shape(a, b) { }
      int area ()
      { 
         cout << "Rectangle class area :" <<endl;
         return (width * height); 
      }
};
class Triangle: public Shape{
   public:
      Triangle( int a=0, int b=0):Shape(a, b) { }
      int area ()
      { 
         cout << "Triangle class area :" <<endl;
         return (width * height / 2); 
      }
};
// 程序的主函数
int main( )
{
   Shape *shape;
   Rectangle rec(10,7);
   Triangle  tri(10,5);

   // 存储矩形的地址
   shape = &rec;
   // 调用矩形的求面积函数 area
   shape->area();

   // 存储三角形的地址
   shape = &tri;
   // 调用三角形的求面积函数 area
   shape->area();

   return 0;
}