40 lines
901 B
C++
40 lines
901 B
C++
/*
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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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{
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public:
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Point(int xx=0, int yy=0) {X=xx; Y=yy; countP++; }
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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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system("pause");
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return 0;
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}
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