创建一个Monitor类,它能知道成员函数incident()被调用了几次.增加一个成员函数print(),显示incident()被调用的次数,并能显示次数的初始值.(Create a Monitor class that knows that the member function incident () is called several times. Add a member function print (), show the number of times incident () is called, and display the initial value of the number of times.)