add class pointer

02.OOP/ClassPointer.cpp

+#include <iostream>
+ 
+using namespace std;
+
+class Box {
+
+    public:
+
+        // 构造函数定义
+        Box (double l, double b, double h) {
+
+            cout <<"Constructor called." << endl;
+            length = l;
+            breadth = b;
+            height = h;
+
+        }
+
+        double Volume() {
+
+            return length * breadth * height;
+
+        }
+
+    private:
+
+        double length;     // Length of a box
+        double breadth;    // Breadth of a box
+        double height;     // Height of a box
+
+};
+
+int main(void) {
+
+    Box Box1(3.3, 1.2, 1.5);    // Declare box1
+    Box Box2(8.5, 6.0, 2.0);    // Declare box2
+    Box *ptrBox;                // Declare pointer to a class.
+
+    // 保存第一个对象的地址
+    ptrBox = &Box1;
+
+    // 现在尝试使用成员访问运算符来访问成员
+    cout << "Volume of Box1: " << ptrBox->Volume() << endl;
+
+    // 保存第二个对象的地址
+    ptrBox = &Box2;
+
+    // 现在尝试使用成员访问运算符来访问成员
+    cout << "Volume of Box2: " << ptrBox->Volume() << endl;
+  
+    return 0;
+
+}
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