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