support bazel complie this project and format code.

practical_exercises/10_day_practice/day3/static_data.cpp

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+/* 静态数据成员.cpp */
+/*
+学习知识：
+静态数据成员
+用关键字static声明
+该类的所有对象维护该成员的同一个拷贝
+必须在类外定义和初始化，用(::)来指明所属的类。
+*/
+#include <iostream>
+using namespace std;
+class Point {
+public:
+  Point(int xx = 0, int yy = 0) {
+    X = xx;
+    Y = yy;
+    countP++;
+  }
+  Point(Point &p);
+  int GetX() { return X; }
+  int GetY() { return Y; }
+  void GetC() { cout << " Object id=" << countP << endl; }
+
+private:
+  int X, Y;
+  //静态数据成员，必须在外部定义和初始化，内部不能直接初始化！
+  static int countP;
+};
+Point::Point(Point &p) {
+  X = p.X;
+  Y = p.Y;
+  countP++;
+}
+//必须在类外定义和初始化，用(::)来指明所属的类。
+int Point::countP = 0;
+int main() {
+  Point A(4, 5);
+  cout << "Point A," << A.GetX() << "," << A.GetY();
+  A.GetC();
+  Point B(A);
+  cout << "Point B," << B.GetX() << "," << B.GetY();
+  B.GetC();
+  
+  return 0;
+}