定义一个日期类MyDate，至少具有私有成员变量：year、month、day，以及成员方法setYear、getYear等（具体隐藏实现方法，用于设置、获取成员变量）、isRunyear（boolean型，判断当前对象保存的年是否为闰年）、print（打印日期对象的年\月\日信息）。-Define a date class MyDate, at least with private member variables: year, month, day, and members of the method setYear, getYear, etc. (hide specific implementation methods for setting, access to member variables), isRunyear (boolean type, to determine the current object saved years is a leap year), in print (print date object \ month \ date information).